Sure, but it wouldn't take a lot of tuning to update a bot to read the animated frames and then you're back to square one. In fact, with 20-odd frames and only three (entirely upper-case!) letters to select it looks very easy to develop a bot that would get a very high success rate.

Actually benefiting from the motion requires a new algorithm. Probably not that hard to design, but not trivial either.

As always CAPTCHA is a game of cat and mouse. When something is completely broken, you need to think up something new.

You don't actually need to use the motion to improve the success rate. Just run the normal algorithm on each frame and elect a winning solution.

Are the people using the captcha-breaking algorithms the ones developing them? Probably not. These things take time... the best way to combat them is probably to change what your captcha looks like and works like every week or so.

They don't really have to be tuned for motion, you can just consider each frame individually.

With this implementation you don't, but it's not hard to construct it such that there is no single frame with enough information to construct the whole message. If you screen capture there are several frames where you really can't tell what the middle letter is, but it's obvious what the message is.

The real issue is a computer can compare the images individually and combine them so if it get's 'G_G', 'GF_', and '_FG' it's going to assume 'GFG'.

In that case you don't gain anything from the motion (except maybe the ability to vote between your bot's output for the individual frames, but that also makes your bot 20 times slower).

Don't people from nigeria offer captcha breaking services for something like $1/thousand now?

Actually makes it a lot easier for BOTs. This one is very easy to break.

motion? just take a single frame and OCR it!