It kind of sounds like your comparing minors to criminals who need a parole officer to watch their every move. I know you were a kid once too. Didnt you hate it when people said kids were immature when you are probably just as mature as the person saying it?
Ones maturity is not the issue here. We're talking about the fact that a minor
probably has limited criminal responsibility. To put it bluntly, it would be more difficult to seek reimbursement if a minor rips you off, than if an adult does (no, I'm not claiming minors are more prone to committing fraud...I'm only stating the ones who do might get away with it with fewer problems). Although I
believe that an adult can enter into a contract with a minor...a minor is allocated more protection. You'd probably have to jump through quite a few hurdles to take a 14 year old to court (they would need a guardian to oversee their defense, for example). I'm not sure about this, though (Lucille...drop some knowledge on us

).
Having said that...I think that (in most cases) implementing this would be a lot of work and/or money. Rich would probably have to create a new usergroup which would encompass minors. Once the minors turn 18, though, they would then have to be placed into the default usergroup. I don't know if vBulleting has a Mod for that, so either Rich would have to do this manually (staying on top of a task of that nature would be ridiculously time consuming), or he'd have to commission custom coding which would do things automatically (but that obviously takes money).
Requiring that minors add a disclaimer would be more plausible. However, that would also be time consuming. I'd have to check the private info of every single user who posts an ad (to verify their age)...and there's no way I would have the time to do that. Rich would probably have to bring in another mod who's only job would be to check the OP's accounts.
Enforcing such a thing manually would be a ton of work. Doing it automatically, however, should be no problem if there is some sort of auto option for that (I'm not too familiar with vBulletin nor programing, so perhaps there actually are auto options for this). The
EASIEST way to do it, however, would be for Rich to disable the option that we all have to hide our birthday. Then, all you'd have to do is check the profile of the individual who you're interested in doing biz with and you'll have their age (or at least the age that they listed).