I searched and apparently you can't add the photos in forum posts, but you can link to them directly.
I still think it's bullcrap. I already avoid any sales posts by people who link to pictures hosted on Photobucket because their site kept flooding me with ads and requests to buy stuff whenever I clicked on a single image, every time.
It's much easier to upload images to photobucket for many many users. There's also users on here with huge photobucket albums not ready to dump them. I really miss photobucket. I could upload 100 pictures in mass via the browser of my choice. Imgur tends to crash on anything over 20 images. It's annoying that I have to break my uploads up into smaller chunks. Still I use imgur because I have to if I want to operate decently in forums. Imgur is hosting for memes that just applied that same ability to everything else. They actually have an iOS app that is just meme browsing.
Imgur won't be around forever either. It's just the easiest to use flavor of the year.
Tumblr is owned by Yahoo, so it'll be nuked any day now, same as all their other crap. Yahoo was already bought by Verizon - and they've said they will block any competing phone provider's email address, because they can, starting today or tomorrow.