Checking Out Some Social Networking Sites

There are many different social networking sites and they are as varied as their members. I'll admit to joining a few but mostly because I had friends who had joined earlier invited me to join.
Some thoughts on the some of the most popular:

MYSpace: Early on designed for teens and therefore not as popular with the over 30 crowd. More recently a venue for bands, and other artists (actors, painters etc.) (established and new) so increased popularity with a wider demographic. Still geared towards a younger audience.

Friendster: This site was popular early (I became a member in August 2003) but has lost ground to rivals. Lets friends make connections thru shared friends, schools, bookmarks of favorite websites and membership in online groups.

Facebook: Originally open only to students and those with a .edu email address now open to all.
Has a robust set of tools and applications to keep users at the site. Users can join networks organized by region, workplace, school, and interest. Has a "twitter" component that asks "what are you doing right now?" that promotes frequent updates and checking by users.

LinkedIn: Considered the premier career related social networking site. Used primarily for professional networking and career advancement. Used by recruiters to recruit and research prospect job candidates.

Also interesting is a site called Spokeo.com that " leverages your existing social network and email relationships to quickly and easily grab content across the web." It checks 41 different social networking sites and the user's email address book to look for connections.