The different uses for social networks

I just read an interesting thread on the NextNY discussion board about why and how people use social networks. The original question was posted by Dan Lewis who confesses to be on the brink of being too old to get "it." Here's my synthesis of the potential uses - feel free to add in the comment section:

* Light communication (Poke, Wall, GlitterText, etc)
* Self-expression: Slideshows, profile, "online identity"
* Dating (browsing profiles and possibly contacting people)
* Finding/ forming your identity, interests, friends, contacts
* Voyeurism
* Sharing photos, videos, text, experiences - with friends and/or strangers
* Bragging
* Playing together (I think this will become a lot bigger in the future)

To me the first two points are really at the core of the social networking experience - that's what seems to be driving most usage. Appreciate any comments.