People could easily share lives with their friends and families long before Facebook. Email, IM etc. But not a whole lot of people seemed to bother with it. Now Facebook brainwashed everyone that it's almost irresponsible not to share.
As much as I want to agree with that, no, it wasn't as easy.
If I wanted to share a picture with 12 people, I had to send 12 emails, or CC 12 people, or BCC them because they didn't want their emails shared with people they didn't know.
Not everyone understood IM, and not everyone was on at the same time.
The bigger question would be why more people didn't latch on to friendster or myspace before facebook. It's as much a social trend as much as a technical one. As computers got cheaper and more people got net connections (or faster ones), there was more of a need/demand for sharing info. Facebook hit at the right time to capitalize on network effects amongst 'regular' folk.
