Got this from Gather.com:

There’s no easier way to start a rumor than online. Don’t believe everything you read. One of the hottest internet search trends out there right now is Matt Damon dead. Don’t believe it! He’s alive, well, and kickin’ it as usual. Why do these rumors start? Who actually believes them? Did anyone out there consider he has a family that could get freaked out by these stories?

Also be careful which links you click through to stories on “Matt Damon dead”. There could be a nasty virus lurking there.