Hey SigTau!
Our nationals requires that any social in which chapter funds is used, have at least one advisor present. Basically she acts as a chaperone. And trust me it's a lot easier for "an adult" to talk the cops out of shutting down a party than a couple of college students.

She also makes sure that everyone has a sober driver and she'd also be allowed to cut you off if you get to out of hand.
Our advisors generally let the youngest one take care of socials. This means that she's usually cool enough to let all the girls have the fun but responsible enough to lay down the law. It's not unheard of for us to finish the icebreaker only to have her very loudly announce that the party is over and she's sure that we'll all leave immediately and not have an after party.

So she "completed" her duty and we get our fun!
The only thing I hate about it is that you have to hunt down someone who is willing to spend her Saturday night at a party where she can't cut loose.
I have noticed though that the fraternities never have advisors present. Personally, now that I'm an alumna, if I were to pull chaperone duty; I would request that the guys had someone there. For one thing, they'd probably listen to him more. And I'd have someone to chat w/ too. If the chaperones are chatting they can't put a damper on anyones buzz.
Every weekend we have sober drivers available. A drunk sister would just call her sober sisters on the chapter cell phone and they'd come get her and her car. We don't have houses at my school, and nobody walks anywhere in SoCal!

So it's definitely a bonus.
We used to do this program w/ a fraternity but there were a few nights that the guys either completely flaked or brought beer along! But mainly the sober girls and guys would either study together, just hang out, or actually hit the town. As long as they were in the county they could do whatever they wanted. It's a good way to start a relationship w/ another chapter so I completely recomend everyone do it.