How can you possibly get into trouble playing with friends? You mean they will resent you offering them EACH an infinity gun? Does that mean you won't be sharing the unlimited funds available to you? You won't be treating them to the jackpot guns that pour out of the slots like water?
You are going to get in "trouble" - with who? The fairy godmother?
It's just you and friends - there's no INTERNET POLICE!
If you're still paranoid, use gibbed (just google it) and edit your saved games, no one will ever know.
But if I was your friend, I'd want to know why the hell you haven't been sharing! Now give me that railer sniper rifle!
I was playing last night with a few friends and we knew automatically when someone was gibbed.
People who play in groups online, want an experience not someone riding in head first killing things with Conference Calls with a couple of shots.
That is boring and ruins people's fun.
You do it all the time, hence why you see no fault in it, because you are biased.