Now I know brands marketing through social networks are supposed to let the conversations flow, but at some point a brand manager is allowed to draw a line and engage in some filtering.

Case in point: I checked out Facebook tonight and saw Pepsi has a group based around its new promotion where you can design a new can. There are 48 discussion topics associated with the group, the first one listed on the promotion homepage being "sex," with 22 posts by 17 people. As Facebook is a closed network, where you need to log in to access the content, screenshots are included below (click to expand).
The post starts on April 4 with someone asking, "Will you have sex with me?" It devolves from there, with responses like, "im sorry to say, but i bet u like to have sex with animals in ur spare time,haha OH, and NO"

That’s the Pepsi Generation, I guess, but there are some conversations out there this brand need not be a part of.