I thought we were always supposed to save photos to our hard drive, and then upload them to a free photo hosting site like shutterfly or flickr.
I never do. I just go to whatever site and copy the properties. If you want the picture to stay around for a long time it is probably best to do it your way. Otherwise they disappear.
For posting of some critical image that I don't want to go away for a long time, say if I had conclusive proof that a letter "proving" that George W. Bush had skipped out of National Guard duty was really a forgery on a modern day word processor, I'd upload that image to the most reliable web server I could afford (and keep backup copies of that image in multiple, off-site, secure, locations.)