Originally Posted by backlinks.us

If the twitter account is inactive for more then 6 months then you have a chance

You can read more about it in this article. I cant post links yet so delete the * signs to get the link

h*t*tp:/*/*fusible.com/2011/06/how-to-get-a-twitter-username-thats-already-taken-hint-its-easy-i-got-mine/