reply to Whoa Nellie
^I would think that avatars on this board work like images on all the websites out there, i.e. they are cached into your memory, hence after the first download of the image, the photo probably won't use up any of your bandwith (for that user of the site), so once a user has downloaded your avatar for the first time, it is unlikely they will need to download it again unless you change it or the file gets cleared from their web cache.
according to the stats you gave us, Imageshack will give you about 70Gb of bandwith per month for your photo, versus the 1.5Gb given by photobucket, so I'd say imageshack was the better host, as it will allow your avatar to be downloaded a LOT more.
there are about 6500 registered users on the site (plus maybe 500 anonymous ones at any one time), and if ALL of them were to download a 11Kb file at the same time (that's 7000 users), you'd need 77Mb of bandwith.
to summarise, Imageshack gives you more bandwith over the month than photobucket, and although it has hourly limits, a LOT more people would have to download the image to put your av offline.