The patent on SIFT is particularly frustrating because it's free for researchers to use so it ends up in every paper that concerns interest point recognition. S

The patent on SIFT is particularly frustrating because it's free for researchers to use so it ends up in every paper that concerns interest point recognition. So if you ever wanted to build an application implementing paper research, it makes it kind of tricky. A fairly decent alternative (although less resistant to rotation) is SURF which isn't under a patent AFAIK.