(1) is indeed a use-case, unless you require more detailed control over playback/pause/frame numbers. In which case a series of png images (for example, encoded into a .css) and animated using javascript could be used. Google uses this for their doodles.

I think (2) is not really a good use-case. GIF is a terrible, terrible format for movies because of the crappy quality and inefficient interframe encoding. Just use a movie format, they're also good at low-res low-bitstream.

Using a movie format means that you either have to provide multiple versions for different browsers or you have to use Flash.

For a four-second clip of a man being hit in the face with a cat I'm not sure either of those is worthwhile.

I'd think CSS sprited PNGs are much preferred over anigif, not just because of playback control but also because of non-shitty translucency.

(2) is used alot by porn sites (So i hear).

Mouse hovers show an animated GIF representation of the 'film' as a preview.

There are decent (and scalable!) spinners in CSS, but it's not an alternative since not every browser supports them.

Firefox and Opera support the APNG format and there is a clever polyfill[1] to add support to all other browsers.

[1] https://github.com/devongovett/png.js

Beyond AJAX spinners, there's still plenty of use cases for simple & easily embedable animations. Smilies, forum avatars, icons, etc.