I presumed they would employ an "image hashing" algorithm of sorts, you know like audio fingerprinting. Then again, with how poorly thought out their solution is, I wouldn't expect them to have considered this. Having said that, even the simple hash blocking would prevent many non-savvy users from uploading. A better solution would be to let the uploader think it went through, but keep the post only visible to him so that he/she wouldn't keep trying defeat the filter.

It doesn't have a worthy alternative except Evernote, which not only lacks free floating textboxes, images, etc., but is also Windows and OSX exclusive. I would totally donate to a Kickstarter campaign promising to create an open, cross-platform Onenote clone...

Which for some reason (used to?) blows up in size with time. I haven't noticed a significant slowdown with time for a while now, been using Win 7 with an ssd. Also, I recall being able to "restore" performance by simply creating a new user account instead of reinstalling Windows itself, which I presumed is because you get a tiny pristine ntuser.dat. But then again, I've been installing a lot fewer junk...