How do you suppose their power and cooling needs are "unique" (i.e. different from any other company that has a datacenter)?
May be less circadian than a typical enterprise datacenter, due to Twitter's global reach and continuous usage during waking hours.
I don't think that's it. Back when I was tracking tweets/sec on twitter's streaming API (which is supposed to be proportional to their real traffic) the pattern looked pretty circadian. Take a look: http://www.flickr.com/photos/hoop2w1/4208393947/
No more failed whale? At least less of them anyhow. That seems like a big move and a good one doing that earlier than later.