There is a link to the terms of service at the bottom of Flickr.com. There are different terms of service depending where you live, but at least the EU one is clear that you retain ownership and copyright, though they may use your content to promote Flickr. I don't know if the US one is different since it only shows me the one for my location.
Photobucket is also clear that you retain rights to your own images, however they have royalty-free license to use your content for any purpose at all. Flickr's terms specifically limit to using your content in the obvious ways (sharing your photos in all the ways you use Flickr specifically to do) and also for self-promotion. So Photobucket's terms are much broader in that way, but they do not own your photos.