user-1: 
For people not familiar with this name -- MathJax is a plugin which converts LaTeX math markup like $X_1^2$ into proper math notation, in this case .

On one hand equations may appear here too rare to justify it, on the other hand it might be useful for chemistry; maybe it is not a desired use of this system, but it is easier to type $H_2O$ than to fight with HTML subscript.

user3971: Can I also point out it can be used to make much better tables than anything else we have?  I think we are limiting MathJax too much if we think of it solely in terms of equations.   I just discovered it was active last night and used it to make the table here:
Factor causing Methicilin-resistance in MRSA?
If you look at the edits, you can see the ascii tables I was trying to make, but I think that came out much better.
Also is it highlighted somewhere other than this question that we can use Mathjax?  I have wanted to use it before and just assumed we didn't have it.  If it is highlighted, I certainly missed it.

user25: It seems like huge overkill for this site.  The only time I'd use it is when talking about biophysics stuff, but there's always Physics.SE.  Getting it enabled on EE.SE was like pulling teeth as the administration was fearful of the tremendous burden it placed on bandwidth.
<sub> and &rightarrow; seems fine to satisfy most casual chemical conversations.

user430: We should have LaTeX support - there's no reason not to unless it burdens the system. That's why we shouldn't use MathJax, which is client-side and will increase the size of every fresh site load.
We should use a server-side option which produces SVGs and stores them. They have an excellent system at Scienceforums, which they have open-sourced here. It's for IPB but could be easily adapted for SE 2.0.

user69: As a compromise, I'd like to point out this tool.  It allows you to enter LaTeX notation either directly or using buttons then download a rendered image.  It works in real time and can be included in answers by copying the URL location then inserting a picture as normal.  
Whilst this is obviously not ideal for those used to entering LaTeX directly, it of course doesn't add to page loading times.  

user1: The basic gist is, a demonstrated need for MathJax needs to be shown before we can enable it. It's a heavy script that we have to load on every page, and on some machines it can cause a hefty loading time. So if it's extremely rare that it comes up in comparison to the bulk of questions on the site, we prefer not to enable it. Consider Stack Overflow, which we still avoid enabling MathJax, because it just has too much slowdown for how comparatively rare it turns up.
We'll be keeping an eye on this question for evidence for and against the implementation of MathJax.

user2: Congratulations, you should now have MathJax implemented here!
[EDIT]: I almost forgot to include -- the TeX / LaTeX guides are all on meta.Math. If you'd like to experiment with the formatting, I suggest using their Sandbox.

user67: Yes, because to be frank, typing out any math without some sort of notation system in the Stack Exchange software is a pain. And I don't necessarily think it's "overkill". While some users might not use it a great deal, most of my work is either mathematical biology or mathematical epidemiology, and talking about predator-prey models, epidemic models, etc. - which don't really have a home to talk about their substance rather than their implementation outside of this site - is essentially impossible without typing out some math.
More to the point, deciding not to have it I think stakes out a somewhat dangerous position that this site isn't interested in questions regarding Biology that require heading into any math more complex than high school algebra.

-1: <blockquote>
  <p>For people not familiar with this name -- <a href="http://www.mathjax.org/" rel="nofollow noreferrer">MathJax</a> is a plugin which converts LaTeX math markup like $X_1^2$ into proper math notation, in this case <img src="https://i.stack.imgur.com/SEU4E.png" alt="enter image description here">.</p>
</blockquote>

<p>On one hand equations may appear here too rare to justify it, on the other hand it might be useful for chemistry; maybe it is not a desired use of this system, but it is easier to type $H_2O$ than to fight with HTML subscript.</p>
 3971: <p>Can I also point out it can be used to make much better tables than anything else we have?  I think we are limiting MathJax too much if we think of it solely in terms of equations.   I just discovered it was active last night and used it to make the table here:</p>

<p><a href="https://biology.stackexchange.com/questions/9916/factor-causing-methicilin-resistance-in-mrsa">Factor causing Methicilin-resistance in MRSA?</a></p>

<p>If you look at the edits, you can see the ascii tables I was trying to make, but I think that came out much better.</p>

<p>Also is it highlighted somewhere other than this question that we can use Mathjax?  I have wanted to use it before and just assumed we didn't have it.  If it is highlighted, I certainly missed it.</p>
 25: <p>It seems like huge overkill for this site.  The only time I'd use it is when talking about biophysics stuff, but there's always Physics.SE.  Getting it enabled on EE.SE was like pulling teeth as the administration was fearful of the tremendous burden it placed on bandwidth.</p>

<p><code>&lt;sub&gt;</code> and <code>&amp;rightarrow;</code> seems fine to satisfy most casual chemical conversations.</p>
 430: <p>We <strong>should</strong> have LaTeX support - there's no reason not to unless it burdens the system. That's why we <strong>shouldn't</strong> use MathJax, which is client-side and will increase the size of every fresh site load.</p>

<p>We should use a server-side option which produces SVGs and stores them. They have an excellent system at <a href="http://www.scienceforums.net" rel="nofollow">Scienceforums</a>, which they have open-sourced <a href="http://blogs.scienceforums.net/capn/2010/08/26/releasing-ipblatex/" rel="nofollow">here</a>. It's for IPB but could be easily adapted for SE 2.0.</p>
 69: <p><strong>As a compromise</strong>, I'd like to point out <a href="http://www.homeschoolmath.net/worksheets/equation_editor.php" rel="nofollow">this tool</a>.  It allows you to enter LaTeX notation either directly or using buttons then download a rendered image.  It works in real time and can be included in answers by copying the URL location then inserting a picture as normal.  </p>

<p>Whilst this is obviously not ideal for those used to entering LaTeX directly, it of course doesn't add to page loading times.  </p>
 1: <p>The basic gist is, a <em>demonstrated need</em> for MathJax needs to be shown before we can enable it. It's a heavy script that we have to load on every page, and on some machines it can cause a hefty loading time. So if it's extremely rare that it comes up in comparison to the bulk of questions on the site, we prefer not to enable it. Consider Stack Overflow, which we still avoid enabling MathJax, because it just has too much slowdown for how comparatively rare it turns up.</p>

<p>We'll be keeping an eye on this question for evidence for and against the implementation of MathJax.</p>
 2: <p>Congratulations, you should now have MathJax implemented here!</p>

<p>[EDIT]: I almost forgot to include -- the TeX / LaTeX guides are all on meta.Math. If you'd like to experiment with the formatting, I suggest <a href="https://math.meta.stackexchange.com/questions/370/formatting-sandbox">using their Sandbox</a>.</p>
 67: <p>Yes, because to be frank, typing out any math without some sort of notation system in the Stack Exchange software is a pain. And I don't necessarily think it's "overkill". While some users might not use it a great deal, most of my work is either mathematical biology or mathematical epidemiology, and talking about predator-prey models, epidemic models, etc. - which don't really have a home to talk about their <em>substance</em> rather than their implementation outside of this site - is essentially impossible without typing out some math.</p>

<p>More to the point, deciding not to have it I think stakes out a somewhat dangerous position that this site isn't <em>interested</em> in questions regarding Biology that require heading into any math more complex than high school algebra.</p>
