I think I figured it out, sorta. I transferred my account to photobucket today - not really because of this, but because they have a spot on your homepage that displays large thumbnails of "everybody's photos", as they are being uploaded I suppose. You have to click on it to get the thumbnails to go away. Well, I've never paid attention to that feature before, when low and behold, there was a nasty pornagraphic pic that popped up. I was so upset and disgusted. That should have been flagged by the user and should never have popped up in "everybody's photos". Bleck. Thankfully, photobucket doesn't have that on your own personal homepage.
Photobucket also has a handy feature where they'll list the url of your pic, modified for whatever purpose you want - images on forums, myspace, etc. I noticed that there was a slight difference in the IMG url they provided, and what it came up as when I simply went to "properties" to nab the url.
For example:
when I grabbed the url by clicking on "properties", this is what I got:
http://i214.photobucket.com/edited.jpg?t=1188878948
whereas, the IMG code they provide is this:
http://i214.photobucket.com/edited.jpg
(nevermind the incorrect techno terms, I probably make no sense when I speak computer.)
Anyway - what I'm trying to say is that I think it has nothing to do with which place you have your photos, but with the stuff that follows .jpg on the url(?).