Playground mentality comes to the (LinkedIn) office, Jessica Guynn, Chronicle Staff Writer

Four square is also a popular social activity at LinkedIn. After scooter races, basketball and Whiffle ball flopped as company sports contenders, the Mountain View online service that connects professionals kicked off afternoon four square bouts on a back parking lot.

"Different people had different recollections of the different rules they played by in elementary school," said Chris Saccheri, 30-year-old LinkedIn director of Web development. "So we made it up as we went along."

Four square has become so popular that in May, when LinkedIn hosted a lunch for fellow geeks at its offices, the company handed out four square balls sporting the company logo.

Now the competition seems to be heating up. Mountain View-based job search engine SimplyHired recently challenged LinkedIn to a four square match.

San Fransisco Chronicle Story