Facebook does not require a picture to create an account.

>The creation of an account is subject to a user's decision. No one is obligated to create an account on a site. However, major social sites, such as Facebok, are having the profile picture at the account creation level. I wouldn't see how a social site could grow without an image linked to an account. Among our new features, the turn around of the site into a more ready to go social networking site is on the lineup.