When I joined Facebook last year, my main goal was to keep in touch with my little brother. He was serving his third tour in Iraq, and since phone time was hard to come by, Facebook turned out to be a quick, easy way to touch base almost daily.
Then he got engaged to someone who I'd never met, and I debated (internally, of course) the etiquette of "friending" a complete stranger. Fortunately, that leap of faith introduced me to one of my new best friends.