Many of these gang bangs posted on Craigslist are iffy, to say the least. First of all, for many ladies, the fantasy is more exiting than the prospect of actually going through with it. Secondly, often a lady has an unrealistic fantasy of who is going to show up: Dr. McDreamy, Antionio Banderas, Tom Cruise... in other words, when she gets responses from real guys who are not tall, dark, handsome with a six pack, they tend to lose interest.
Thirdly, these ladies forget that getting a bunch of guys together on short notice does not work.
That being said, there are a number of gangbang events every month in the Bay Area. these are almost always organized a week (or couple of weeks) in advance. The organizers tend to do this for a living. There is almost always a participaton fee. Expect to pay anywhere between $80 - $100. Often there are two or more girls being serviced. This is supposedly for the food and snacks, and to cover the hotel room, though my calculations show that often, the organizers make a lepping supplies) profit. Usually they give the participating lady a little tip.
But having organized a few GB's myself, if you take into account the time spent to organize such an event (on average 20+ hours answering emails, running around buying and schlepping supplies to the hotel room, etc), such a fee starts to look more and more fair. Don't forget, if only a few guys show up, the host loses money. I am always glad when I break even.
It is really not that weird to participate in a GB. I mean, when you go to the gym, you are often naked in front of other guys when you take a shower. No big deal. And often, there is less presuure on the guy because ket's face it, you don't have the responsibility to get the lady off. If you don't give her an orgasm, no big deal. Another guy can take care of her. Also, you don't need to have deep discussions with the lady. It is pretty much a physical in and out affair.