Apparently Apple CEO Steve Jobs invited Facebook CEO Mark Zuckerberg for dinner at his house to talk about Ping two weeks ago, according to the Los Angeles Times, That's when a tipster spotted them on a stroll in Palo Alto. Apple has been trying to reach a deal with Facebook, after the later dropped their integration into Apple's Ping music-based social network at the early-September launch.
LA Times quote:
"They are two of Silicon Valley's most famous founders: Jobs created the world's must-have gadgets, Zuckerberg the world's most popular social networking service. These days they are often mentioned in the same breath. Now apparently the two also recently broke bread."