I've mainly played 3 online games.
Runescape, when I was young. I never actually was able to trust anyone, and in hindsight it was probably because of the maturity level.
Sword2, now it's current name, I had probably the biggest friend list in the game, I knew close to all the known players. However I was only actually able to trust one person entirely. This trust was for the most part reaffirmed when he shared with me a glitch in the game, 'item duplication'. This would probably be the most trusting 'e friend' I've had if you like.
Combat Arms, I made a group of 'e friends'. I trusted probably one to an extent, but never let anyone play on my account, despite having played on others. I was gifted around $200 in total on this game, and had I think the best account in the game for a f2p player.
Now answering your question, with all my 3 aforementioned points in mind, I've only managed to trust 1 person entirely and didn't get screwed over by him. So yes, you can trust a very exclusive club of individuals, however for the most part when you play a game like RuneScape, it is a very individualized game which fuels the act of 'luring', 'scamming', 'stealing' all kinds of that behavior.
However, I never kept in contact with any of my 'e friends', which just reinforces the point, your only 'e friends' to play the game thats it. Everyone has a bribery point if you like, and if you make it too easy to resist a large temptation, most people online would snap at it without second thought.