The world of widgets is best when viral in nature. Photobucket and many other photo sharing websites allow users to post their photo album on other social networking profiles. Click on the photo and you are taken directly to the user's Photobucket profile page. What a great way to market your website with word-of-mouth on the Internet.
The Internet community is also more likely to trust a friend or "person like them" when choosing services and products on the Internet. This is a great way to do just that, advertise a photo sharing website advertised by people just like you.