Client side resample ? I would love to know how they do that. With AJAX it does not seem possible.

With Javascript (AJAX) it wouldn't be, but with a little Java or Flash it is. (I'm not 100% sure on Flash, but I bet it's possible)

I think Facebook uses Java for this bit (not totally sure, and I don't want to have to log in just to check)

Facebook uses the Aurigma Image Uploader, which is implemented both in Java and as an ActiveX control.

you can't access uploaded images in flash. you have to send the full image to a server, then re-download it, do your manipulation, and then upload the final version.

particularly annoying when uploading to S3, since you have to go client->server->client->server->S3.