I received a bunch of animated GIF files through iMessage recently, and I noticed one "didn't work". I saved it to my Dropbox and viewed it on my computer. The filetype was now suddenly JPEG and all but one frame were stripped. On the sender's end, though, it was still in its original, working GIF format even after being delivered. So I guess there's some compression going on "in the cloud". We also tried sending a regular photo from the built-in camera app, and it came through at 1152x860 pixels and 440kb. Too small both in resolution and size for an iPhone 4 rear-camera photo. After some trial-and-error by sending various sized images back and forth, I think the max file size before compression is 500kb. What other (if any) limitations are there to attachments in iMessage? Do they only apply if you are on 3G or also on Wi-Fi for example? And lastly, is it possible to bypass the compression?