I think it's great but there needs to be an awareness of emotional involvement - if it's with people you don't really know (providing you have a history of their health etc.) then fine, if it's with people you're already in a relationship with (like menage a trois and polygroups) then that's also fine. But when it comes to experiencing this sort of thing with friends...yeah it can get tricky. I think it takes rather a lot of trust to be honest - even people you don't know so well can make known such experiences quite easily these days...i wonder how many people have ended up on pornographic websites without even realizing it. There's a big market for threesome videos etc.

Personally i prefer this sort of this to be kept within a poly relationship - sex is better with people you care for anyway.

Just make sure everything's safe, sane and consensual.