Reunion Romances: Remember Me?

I just finished reading one of my favorite types of romances -- the reunion romance.  It was wonderful!  There's just "something" uniquely appealing about characters who have known each other intimately in their past being thrown back together.  Or maybe a lot of "somethings."     

My short list of the reunion romance "somethings."

1. "Remember me?"answered by "How could I forget?"  It's knowing you're getting a story that has one of the best questions and answers in romance.  (Or is that two questions?)
2. It's the appeal of second chances.  Yep, that seems most likely, but it's more than just retracing steps. 
3. It's the back story.  Yes, sometimes I like back story.  Actually, that's one of the rather unique things I think is so great about a reunion story.  I know I can expect some "shared baggage" and I kind of like that. This kind of baggage is shared memories.  They formed a bond that's still intact, and I want to hear about it. 
4.  It's the lure of unfinished business.  I'm curious as to why these two split up in the first place.  Or, for that matter, why do they have a chance now?  What has changed? 

 And that's several things I can think of on the appeal of a reunion romance.  Or maybe it comes down to one other "something."  I really can't stand not knowing how something is going to be fixed.  From the start, I know something has broken and I just love knowing it's going to be put back together again.