system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Why didn't Voldemort recruit members with the unbreakable vow instead of the dark mark?

Or both, if he wanted. Surely he'd never have the problem of spies and traitors with a vow along the lines of "I swear never to act against an order given to me by the dark lord himself". I think the vow can be that general, since Fred and George Weasely were caught in act trying to make Ron swear never to tell their mother about something they did.

Okay it may be in the dark lord's favour that his followers were able to hide and lie about their membership when he was vanquished by Lily's protection, but Voldemort doesn't strike me as the sort who plans for his own defeat so why didn't he enforce the unbreakable vow?
gpt
Unless they are very specific there is a big chance of accidental breaking of a vow. Say that the order is "kill Cornelius Fudge". It's supposed to be an intricate plan, executed perfectly at a certain time.  And then you see Fudge at the pub. Now you have to kill him, no matter that you're screwing up the plan - do you turn around and die, or do you screw up Voldemort's plan by killing the man right then and there, just to live to be subject to his wrath?

It's basically a magically (as opposed to legally) binding contract. Contracts have loopholes, misinterpretations and ambiguity *all* the time. And then you're dead.

A system where Voldemort, the Dark Lord, has to *watch what he says* probably wouldn't appeal to him in the slightest.

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In addition, he likely holds that death is far too gentle a punishment for betraying him - and that people know it.

There are probably even more possible reasons.