How Do You Choose Your Site?

When you decided which social networking site was right for you, how did you decide? Did you just choose the one your friends are using? Did you choose MySpace just because it's the biggest? Did you seek out something specific like a social networking site for parenting or weight loss or something else?
There are lots of reasons to choose a social networking site and to want to network online. What brought you to the social networking site of your choice and why do you network online in the first place?
~admin