I bet I'm not the first person to put up a post on this topic. I expect there must be hundreds of post like this one, trying to tell people from making their social life interfering in their professional life. The two things are meant to stay separate, no matter what. I've seen friendships turn sour on this note more than once. It's always the same. It always starts with two people working together. Those two apparently are friends too. Then after a while comes a time (this moment ALWAYS comes when things like this happen) when one of the friends tries to take an advantage of the other for professional help. Now a little hand here and there is cool, no one minds. But what does get troublesome is when someone expects "favours". Favours not involving the other person entirely and may put the other friend in jeopardy. By the above I mean stuff like, him completing the assignments in the name of friendship while the other "friend" goes out to enjoy his life. Or in college when you have to sit through a particularly dead boring class while your friend is out relaxing. Feels sorta bad.
The worst is when you work as his team leader and have to assign work to him. That's when things get most dangerous. You try to assign everybody work (including yourself) and there you see your "friend" laying off cause he knows you. When you ask him to do it, he takes you for granted. When you have no choice but to order him to do it, suddenly it's an ego problem and *POOF!!* there goes ages of friendship. Who is at fault here? The bossy friend or the "I'll do it later" friend?
Such things came to line with me during an engineering competition we were participating in. I tried telling people (classmates) to get to work. I had finished my part ages ago and the whole thing was stuck cause of three guys doing stuff at their own pace. We had a deadline. A very tight deadline. The only way to get them to really get them to work was to get all bossy (my friend, also our team captain did that). Not very pleasant, but had to be done. Even that didn't help much. But it sure got them working faster if with a scrowl on their face. We barely got the design ready in time for the event. But my friend did end up getting all sorts of criticism from other about how he's an equal, even if he's a team captain. But everybody failed to see the end result. Awesome it was.
Whatever the case may have been, it was a sad scenario. Friendship is best kept at a distance, or if you look at this in another way, atleast you get to know people are true to you and won't use personal connections to get their work done. I always say that unconditional friendship is the best. Pure emotion and understanding. No messy business. Work and friendship is best left alone, unless the situation get really bad and I'm sure a true friend would never back down from helping a friend in need...