Only /b/ has no rules (There’s actually some rules that are enforced, e.g. no posting illegal content), and that also applies to moderation. As in, a moderator can just ban you for any reason they want.

It isn’t sustainable. No clerk will take the bet more than once. Also, the clerk doesn’t have to take the bet to interpret it as bribery and call the cops on you. In addition, there’s the risk of the clerk simply not honoring the bet.