There is a real Anna - she's a girl from Australia that Duritz met on vacation in Greece in 1989, and she broke his heart. Duritz was far from famous at the time - he saved up money doing landscaping work to afford the trip. At the end of the trip, he and Anna agreed that there was no way for their relationship to continue, and they went their separate ways. "The characters keep saying 'I'm not ready for this sort of thing' until at the end when they find out what they really aren't ready for is the loss, but then it's too late," Duritz explained.
Adam says that they remained friends and occasionally spoke on the phone, even after Anna got married. She is a big fan of the song.
Beth - Charleston, SC, for above 2