It's not clear how it started, but a ridiculous rumor that Facebook is shutting down is spreading fast on social networks.

The hot rumor -- evidenced by Google Trends and gaining traction on Twitter -- says that on March 15, 2011, Facebook will be closing down. Not taking a day off, not undergoing maintenance, but ending entirely.

The rumor has led to such frantic tweets as, "Facebook will be shutting down on March 2011? I hope not!" (@MissAyl) and "So the rumor is Facebook is shutting down....please don't jump to twitter & ruin my social networking experience" (@jjelksboss).

Facebook users are also concerned. Says one: "Facebook is shutting down on March 15, 2011 for good D: Is there any way we can stop this!?!?" And a group has already started to stop Facebook from shutting down.

Ironically, Yahoo announced last month that its "Yahoo Video" will be closing down on the date in question, March 15, 2011, and videos can be seen for the last time on March 14. But that hardly means it's taking the rest of the Internet down with it.

Just a day ago, an opinion piece published on CNN said that the recent Goldman Sachs investment was the "beginning of the end" for Facebook. That post went viral with more than 5,000 Facebook "likes" and could be partially to blame for the ensuing panic.

Whatever the reason for this rumor, it's safe to say that as a site with more than 500 million users and a $500 millon investment from Goldman Sachs recently, Facebook won't be shutting down anytime soon.

UPDATE (3:30 p.m. ET) ABC News speculates that the rumor started with this post published Jan. 8 by the satirical Weekly World News. Facebook has yet to officially respond to the rumor.

UPDATE: (6 p.m. ET) Facebook has officially responded to the rumors with a tweet: "We didn't get the memo about shutting down, so we'll keep working away. We aren't going anywhere; we're just getting started." A company spokesman also dismissed the rumors as "silliness."