This is a pretty amazing example of using Twitter. The other day I twittered (tweeted?) a little rant about Firefox 2 ignoring embedded color profiles in images, so that images are displayed too dark. Only a few hours later user firefox_answers replied to my little rant with a link to a page describing the problem and that it is fixed in FF3.
They track the keyword “firefox” to see what people write about their product on twitter. I think this is pretty good pratice for any company somehow involved in the web industry. Thumbs up Firefox team!