Oh, that Ice Bucket challenge. Everybody's doing it -- and we mean everybody.
Gavin Newsom, Chris Christie -- and now Mark Zuckerberg.
For the uninitiated, the challenge, which is intended to raise awareness and funds for the fight against ALS, or Lou Gehrig's disease, works like this: you dump a bucket of ice water, cubes and all, on your head. Then you donate some money -- and challenge other people to do the same.
The Zuck was challenged by Christie, the New Jersey governor who also issued the call to New Jersey Sen. and Silicon Valley favorite Corey Booker.
After Zuckerberg took the plunge, he challenged Microsoft founder Bill Gates, Sheryl "Lean In" Sandberg and Reed Hastings.
You could be next.