Twitter (Twitter.com/BermanPost) has now rolled out some Verified Accounts.
"To prevent identity confusion, Twitter is experimenting (beta testing) with a 'Verified Account' feature. We're working to establish authenticity with people who deal with impersonation or identity confusion on a regular basis. Accounts with a are the real thing!"
You can find an example of a Verified Account at http://twitter.com/CV31.
As I opined before (Berman Post: Twitter to Roll Out 'Verified Accounts'); this should efficiently bolster the credibility of the verified accounts but may also reduce the credibility of people/accounts who are not considered important enough to be verified or are lower on the verification list while they are waiting their turn.