Until now, you couldn't remove users from the list of fans, but Google changed this: if the list of fans includes spammers, you can block them. Users "will be blocked from commenting on your photos and adding you as favorite. Blocking someone cannot be undone," mentions a warning. You can also block users who post offensive comments.
Picasa Web Albums added a list of "suggested favorites", which includes all your contacts that use Google's photo sharing service. It's a good opportunity to find interesting photos uploaded by your contacts and to add them to your favorites.
But if you can add users to a list of favorites, why is there no option to favorite images? Picasa Web added a link below each photo: "I like this" and the number of likes, but you can't keep track of the photos you like.
