I wouldn't consider a situation with booze and lots of girls or even getting hit on while really drunk to be high risk situations. A high risk situation to me is when sex is an immediate option.

I was in Vegas one time with a friend, and we had been hanging out with some of his other friends, including a quite gorgeous lesbian girl he was sharing a hotel with(this friend was gay as well). My girlfriend had left a day early so she could study for a test and I went out with all of them the last night. We had to leave super early so we crashed in his room after partying, the lesbian girl was still out partying when we went to sleep.

I am woken up a couple hours later to the "lesbian" girl(lesbian now in quotations) telling me to take off my pants because I looked uncomfortable. I thought she was just being nice/playful because I still at this point thought she was, well, a lesbian. Same reason I didn't think much of it when she climbed into bed next to me, it was her hotel room anyways. Next thing I know she is rubbing her hands all over me and feels that I have a huge erection because a gorgeous girl is now basically fondling me, and more or less tries to make a pass at me right there.

I didn't do anything with her but it was the most tempting thing I have ever experienced. It took an unreal amount of self control, because I was already in my underwear, with a gorgeous half naked girl lying next to me. I always told myself I would never cheat and I still haven't, but that encounter made me realize it's a lot harder than I thought it would be when sex is literally right there for the taking.

Now, those are pretty extenuating circumstances. If I hadn't thought this girl was gay, I would have gotten up and slept on the floor the second she initially woke me up. That's how you avoid cheating - you avoid those situations, which is exactly the point the person above you was trying to make.