I signed up with photobucket and a friend of mine uses Fotki:
http://www.fotki.com/us/
PictureTrail has been around since 1998:
http://www.picturetrail.com/
Probably the best thing to do to protect yourself is to google the service you're thinking of signing up with to see if anything negative comes up but as long as they only ask for an email address and username to sign up with, I don't think there's much to worry about but better to be safe I guess.