I wouldn't put it past Tony to believe he knows something which in reality he only guesses at. Although he has been privy to secret information in the past too. I think lots of people trust him with secrets, and generally with good reason it seems.
It's true that people entrust me with things and in return i sometimes entrust them.
In Med's case she would tell me things but often comes out with it anyway, so at that point I'm free to speak openly about whatever she told me.
Whenever I come out with accusations about things i don't know, it's really a tactic that increases the odds of finding the truth.
Though sometimes when I do that I'm sure. I've been criticized for displaying good intuition, which in a sense end up working out for me.