SAN FRANCISCO CHRONICLE — Oct 23 — There's now a social network site for practically every subgroup. aSmallWorld.net is an invitation-only site for jetsetters. Dogster.com caters to dog owners. LinkedIn.com serves professionals. Friendster has about 19 million users. MySpace.com now boasts 33 million users. Facebook.com has grown to 8.3 million users and is the 11th most visited site on the Internet. Among other things, each site is a treasure trove of consumer data. In May 2005, the Accel group, a Silicon Valley venture capitalist firm, bought a $12.2 million chunk of Facebook, which is currently valued at around $100 million. This month, Yahoo purchased Upcoming, a site that lets people publicly list and share their schedules of events with friends. In May 2005 Google bought Dodgeball; a site that brings social networking to mobile phones. 'Online social networking is in its infancy. There's a huge opportunity for players like Microsoft or Yahoo or Google to layer social networking applications on top of existing features, like utilizing existing buddy lists or saving e-mail addresses and connecting them to profiles. 'Social scientists ascribe the appeal of social networking sites to what they call "low cost." Rather than engage in long conversations to determine someone's favorite movie, for example, Facebook users can just glance at a profile and get a sense of the interests of the person living next door. But lots of low-cost friendships might mean lots of lower quality friendships. FULL ARTICLE @ SF GATE
Mark Brooks: Some social networks will morph into or be created as Personal Information Management systems to complement the likes of Outlook (or CRM, in the case of LinkedIn) to allow people to orgnise their networks of friends more easily. Many social networks spur on the 'connectors' to connect with as many people as possible, turning their networks into popularity contests. This creates a low focus, low integrity network. Facebook is the best example of a high integrity, high utility social network; they masterfully limited connections to a core group of students/alumni. This will ensure their success well into the future…and give classmates a run for their money. Social networking is indeed still in it's infancy.

I was wondering you left out a few sites. Flickr, SpRnch.com and Hi5.com
These as well are really nifty!
@ Lisa: Sprnch.com would not fit into these categories because sprnch is almost like a phonebook slash profile slash networking site. People don’t sit on sprnch at all I find. It’s more a set up your page and when you get a call you see who it is enviorment and boom a connection. Different vibe almost like an answering machine for the net.
I signed up there and was thrown how it was designed. Simple and maybe the idea are ahead of its time. Could be a good or bad thing for them.