system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly is 'Obamacare'? What is it supposed to do? And why is it so controversial?
gpt
one of the most controversial aspects is the mandate that everyone **must** have health insurance, or face tax penalties.

here is the rationale:

hospitals must treat sick people (or people that need emergency treatment) even if they cannot pay (because they are uninsured and cannot afford the sometimes $1000s of medical bills).  The hospital must re-coup the cost of treating these people by getting reimbursed from the government (tax dollars) or having the people who *can* pay pay more.  

"Obamacare" forces everyone to have insurance, so everyone *can* pay because their insurance will pay for them.  Some people don't have jobs that offer health benefits, and cannot afford to buy private insurance.  To solve this, the government offers need-based subsidies to all of those people.  The government already does this for extreme poor (Medicaid) and the elderly (Medicare).  

**Proponents** say that this will drive down the average cost because insurance companies divide all of the costs amongst all the people in the "insurance pool".  So, if there are a lot of people in the insurance pool, the average cost is less for each person.  They also say it will drive down the overall costs because of **preventive health care** like going for an annual physical or cancer screening, which an uninsured person would otherwise not go to (and therefore only be treated when the shit hits the fan).  

**Opponents** say that it is constitutionally invalid because the government cannot force every person to buy a private good like insurance (just like the government cannot force you to buy an American-made car).  They also argue that its a "state's-rights" issue, and that the decision should be on a state-by-state basis.  Opponents of the law would say it would cause an increase in health care because of the bureaucracy (it would take out profit margins) and because people would **"free ride"** or obtain healthcare services that they do not really need because they are not paying for it.  For example, opponents might say that every Jane Doe will go rush to the doctor everytime she gets a cough, and there would be tremendous lines at the doctor's offices and hospitals since people are not paying out of pocket.