Never trust anyone at work. Supervisors, subordinates, people on equal ground, or even anyone that you consider a friend.
At my previous job that I was at for 8 years, my immediate supervisor became one of my best friends. Hanging out all the time away from work, large group of mutual friends, etc. My work had a no-dating policy if you had any sort of influence over their position(i.e. manager/employee), but you could date as long as your positions never interacted within the company. I started dating a girl I met, told my boss(my friend) about it immediately on the record, and even went to HIS boss(our regional director) and told him immediately about it. Confided to both after just 1 date what was going on, to tell me right now if it was a problem and I would cut it off, etc. Both guys were fine with it.
Fast forward 2 years and I'm living with the girl, things are pretty serious, and we still don't work anywhere near each other(not even at the same physical location, we work in opposite sides of town). I have to fire one of my employees for basically gross incompetence and repeated poor performance(with months and months of write-ups and documentation) and he immediately calls our corporate HR to file a complaint that I only fired him because my "girlfriend" didn't like him. I think she had actually met him maybe twice. I basically get an ultimatum from corporate HR that we either need to cease the relationship, or one of us needs to find employment elsewhere. Well, at this point we were living together, so just randomly breaking up wasn't an option. Both my boss(my good friend) and his boss(our regional director) played 100% dumb like they never knew we were even dating. I took the high road and didn't throw my friend under the bus, even though me and my girlfriend had been to his home dozens, if not hundreds of times together. He did not return the favor and fess up that he OKed anything.
I ended up quitting, I had more experience and could find other equal employment easier than my girlfriend could, even though I had been advancing and getting promoted quickly at my current job, and had a great reputation there. Starting over somewhere else and building up that reputation again would take some serious time.
Then 6 months later she cheated on me and I threw the bitch out, so I was real happy about leaving my job for her at that point, lol.
At my current job, I am pleasant to people in my office, but I have no desire to be involved with any of them socially. I don't do things with them after hours, I barely even speak to them unless it's work-related. I don't want to know about their family, and I don't want them to know much about mine. I will always keep work and social life seperate from now on, only bad things can come from combining the two.