We spent some time not long ago evaluating a piece of software called Confluence. It's a cool intranet engine that lets you share with colleagues through wikis.
One of the guys playing with the software got frustrated that it wouldn't let him do something complicated with HTML and, as you do, he tweeted that Confluence was winding him up. Just throwing the frustration out into the ether along with eveybody else's random thoughts.
Sombody at Confluence picked up that there was a tweet about them, and mailed back directly saying yes it could be done and here's how. You don't forget service like that - we hadn't even asked for help and a small negative PR message on Twitter turns into two vocal advocates for Confluence.
Is this a small company thing? I have to say I think it is and there's a good chance that Twitter will work best as a tool for smaller companies - either extremely local or extremely niche, or both. The long-tail without a body.