It's not just the cloud-- the gears too.

Pretty sure there's a Google property with the same cloud + gears loading animation. Blogger, or Tumblr or Blogspot or one of those.

I think its the blogspot theme with the gears in a box that your thinking of.

http://googleblog.blogspot.com/

It isn't the same but Mega uses their animation in the same way.

SingleHop uses a very similar cloud + background icon motif (be it gears, a server or another object) throughout their site as well. Seems to be fairly common.