Well, this is always a fun topic. Here’s my own experience, for what it’s worth:
I had a close guy friend in college. (More than one, actually, but that’s beside the point, as I didn’t sleep with the others.) We really were just friends. Both of us had several long term relationships throughout college. We weren’t particularly attracted to each other sexually and the issue never really came up- until we got drunk at a party.
See, we lived together (with 8 other close friends) and had thrown a huge bash. Both of us got sufficiently hammered and decided to call it a night. We were sharing a room at the time. After sitting around and talking for awhile, he blurted out something like “You know, we’ve known each other for a pretty long time. Do you ever wonder what it would be like to…you know.” I answered something like “I hadn’t really thought about it.”
We were both free of signifigant others at the time, so we decided to give it a shot. No strings, no relationship, just sex. It was okay. We went ahead with it for a few days, got bored and stopped. Life went on as usual.
A few years later, we both broke up with our long-term SOs in the same week. I was at his apartment and ended up staying the night because I didn’t want to walk home that late. We decided that, as we were both horny, we might as well. So we did. The next day, things went right back to normal. It never came up again.
We’re still very good friends. It didn’t change anything. However, if either of us had been even a slightly different person, I don’t think it would have ended as well. We were both stricken with a kind of “relationship apathy.” In other words, we were too lazy and selfish to want real relationships of any sort. Thankfully, we outgrew that phase and found happiness elsewhere.
I guess my point is that “fuck buddies” can work out perfectly well, but I think it’s a rarity. Hell, the last time I tried to have a “fuck buddy,” I ended up marrying him. We’re happy and I’m glad it ended up this way, but I still laugh sometimes and think “THIS wasn’t supposed to happen!” Aside from the occasional one-night stand, all my other experiences either ended up as some sort of relationship or a situation where feelings were hurt.
My advice is tread carefully. Sex is a great way to lose a friend.