If the gif is big enough, which most of mine are, Imgur can output the file as both webm and gifv (simply by changing the URL). Most of the animations I post are outputted as webm's when I upload, but I change the url's to gif so as to not lose quality. I'm not sure if you referring to hosting means something else than what I'm thinking though, so I might be off base.
Unless it's a pretty crazy circumstance, I don't want to use webm. The further loss in quality on top of already losing quality on the gif is too much of tradeoff for me just to get the filesize significantly down. Also, if I'm not mistaken, other places where I post these animations too, such as Tumblr, don't support webm yet.