It could be a wedding, so guests can contribute their photos of the big day, or a public group devoted to pictures of your neighbourhood, your favourite hobby, or even objects (scooters, peeling paint, muscles...).

BBC: NEWS | UK | Magazine | I'll show you mine...

Two members of the group, who identified themselves only as "John" and "Liu, " told CNN in a phone interview that a core group of six people on three continents worked to unlock the iPhone as a hobby.

CNN: Code to unlock iPhone cracked

"I call it Homebrew Health, " says one angel investor, alluding to the Homebrew Computer Club of the 1970s, the group of electronic enthusiasts, including Steve Jobs and Steve Wozniak, whose technology hobby led to the birth of the personal computer.

FORBES: On The Cover/Top Stories

The trade group for wireless networking technology is about to put an end to its members' favorite hobby, network joyriding.

FORBES: Magazine Article

In the U.S., analyzing party platforms is an arcane hobby, like talking in Klingon--generally understood to be pointless, and ignored outside a tiny group of enthusiasts.

FORBES: Commentary