Currently gif images aren't supported as we currently rely on GD as Darko mentioned. Once Imagemagick support is added, we might support gif in the future
Thanks Mark and Darko Imagemagick is installed and working well on our server with other extensions and also Easyblog.
Personally I think it a necessary requirement. In accordance to all our marketing surveys videos, images and gif's are at the top of the list of items that people want to share.
Generally speaking some extension use the approach of not processing a gif upload and therefore the thumbnail production is bypassed the original image is used instead. This would be an easy way to give the required support.
By the way animated gif's that are published in Easyblog or K2 do remain animated in the Easysocial stream.
From a performance and usability point of view, consider a static image for thumbnail that will swap to animated on hover, click or page scroll.
Otherwise you'll load huge animations and slow down your site.