Twitter’s SEO Mistake

Like most web-savvy people out there, I like to perform the occasional vanity-search by googling my own name. In my case, however, I feel it’s somewhat justified because (ready for this rationalization?) managing a web-presence is what I do.

During one such recent ego-google, I came across what I believe is a big mistake committed by our old (new) friend Twitter.

Twitter’s mobile version is showing up on SERPs. Correct me if I’m wrong, but doesn’t this mean a HUGE canonicalization error on their part? Not to mention duplicate content. I’d heard recently that Twitter pages had taken a hit in Google SERPs lately. Is this part of the reason?

I think Twitter dropped the ball here. The thing is, I can’t figure out how. I checked out Twitter mobile’s robots.txt file and it appears to be doing everything right… right?

Can anyone shed any light on this situation?