It's interesting how many upvotes this is getting in a very short time. However, I don't think the average Twitter user cares about performance and URL elegance, so I doubt Twitter will change anything.
I have seen performance issues and outright broken behavior with Twitter's hashbang ajax loading scheme. In that respect, regular users will care (they just won't necessarily know what is causing the issue).
Considering that twitter is the main reason for the spread of the abomination that is URL shorteners you're probably right. They don't seem to care about the health of the web.