First it was Craigslist introducing a real life monitoring on posted messages to its new Adult category. Now it’s Twitter’s turn. The micro-blogging company is planning to crack down on celebrity impersonators who post messages on the service.

One of the appealing aspects to Twitter is that it’s 1-2-3 easy to create an account. But that meant that anyone could spoof a famous person.

In a notable example, St. Louis Cardinals manager Tony La Russa went so far as to sue Twitter last month in San Francisco Superior Court for allowing an impostor to create an account in his name. (The account was subsequently deleted.) Musician Kanye West has also complained. An account in the name of the Dalai Lama was suspended earlier this year.

The verification service will go live this summer. Accounts will receive a “verification” seal so users will be able to see that they are legitimate.

One open question: what constitutes being a celebrity? Britney Spears, sure, but how about Brian Blum?