If they run across any pictures that are "offensive or pornographic," they delete or lock entire albums/accounts.
But most likely you fell victim to a recent server problem they had:
Update Friday Oct 1st 8:00 AM MST
All the albums have been recreated and everybody should be able to login now. If your album is empty, you were one of the people effected by the loss and you will need to re-upload your pictures. We are very sorry for this inconvenience. We always tell people to make sure they keep backups of everything and this is why.
Thursday Oct 30: Unfortunately Photobucket.com has suffered a catastrophic raid failure. This morning the same array that had been giving us problems earlier, crashed. We use Raid 5 on everything but the logical volume was corrupt and unrecoverable. We are rebuilding the disk now and then will recreate all of the albums which should be done late tonite. You will need to re-upload your pictures. If you had a paid account, we will refund your money or add 3 months to your subscription end date, whichever you prefer. This is a sad day for all of us here at Photobucket.com. The albums effected were V's v465-v499. We are truly sorry to those that lost their albums.
The Photobucket Team