I have a particular friend in Pocket Legends who I trust over anyone. However, even with him I've got to be careful because I never know if somehow his account got compromised and someone is faking to be him. You've got to be very, very careful when dealing with anyone. Generally it helps to have some set principle like for example never giving someone anything without an item or gold matching the value as temporary compensation. Just let your friend know it's nothing personal, but merely a principle that you strive to stick to.

Sorry, didn't mean to turn this into a "how not to get scammed 101" but I felt I should speak up and give some words of advice considering I've never been scammed in my entire 3 1/2 years playing this game.