For example, you start a site for college students and you decide to move to the Valley for the summer to work on it. And then on a random suburban street in Palo Alto you happen to run into Sean Parker
I thought that was the fake movie story, and in real life Sean Parker went after Facebook, flying to Harvard to meet Zuckerberg and eventually convincing him to come to Silicon Valley.
I think the flying out to meet Zuck part is true, but it's also true that he later bumped into him that summer in Palo Alto (not sure if they'd stayed in touch).
I read something more along those lines in an article about Sean Parker talking about how he was more involved with things than the movie presented. I can't find that article anymore. Here is an article that actually has a quote from Zuckerberg, stating he let Sean Parker crash at his place (although Zuckerberg himself does not say he bumped in to Parker): http://www.fastcompany.com/magazine/115/open_features-hacker...