First result for the google search 'Twitter' isn't Twitter.com

Uh, yes it is? At least for me.

You're link is broken. There's a "q=twitter#sclient=psy..." and "q=twitter" in that URL. Did you break it on purpose? Or did Google mess up? If you remove the "q=twitter#" it works fine.

I searched it from firefox search box. Interestingly, it's now showing twitter.com for the same search. Definitely, ff is playing foul here.

My first result for 'twitter' is indeed twitter.com.

it is for me.

That's pretty interesting - I guess search.twitter.com is getting links at a better exponential rate, and that matters to google a lot. Thanks, while this could be a one-off thing, it's worth investigating for its implications to SEO.