What to do, what to do?

Question... When you break up with a guy do you have to break up with the friends too? So here is the situation, you meet a guy or girl who is great (of course they're really a heathen, they just trying to trap you). As the relationship progresses you start to meet their friends and their friends are great. You become particularly close to one of the friends and you guys just start hangout together outside of "date" stuff with your other. Well eventually things with the other start to fall apart and the friend is there for you and still wants to be friends despite the fact that they are still friends with the other. You really like their friendship too and don't want to lose that. But then things get sticky. What about when your ex finds a new person, then your friend is going to all the old hang out spots with your old guy and their new interest. How suckey is that? Or what about when the friend plans some big party and you know your ex will be there. What if your ex shows up with his new person and you are there too. It could make for a ton of very awkward situations. So what do you do? Do you have to lose the friend when you lose the guy or is there a way for this situation to work out for the best?