Why should google go out of their way to fix shortcommings of anothers website, twitter will be brought extra traffic by those not using twittersearch and google has nothing to gain by replacing twittersearch.
Twitter's goal should be "to properly use html tags/properties in a way that does not ruin search results". If Twitter provided no meta description, Google would be forced to create their own description, which you could then blame them for getting wrong. Instead, Twitter uses the tag inappropriately, which Google trusts.
This isn't Google's problem; it is Twitter's. Whether or not Twitter cares is a different story entirely.
Whether twitter cares or not, Google should care. That's what this issue boils down to. It's a problem with the Google user's experience, not the Twitter user's experience, despite who's fault it is.
