Athletes from every sport are on, a website that asks one question, “What are you doing?” Answers must be under 140 characters in length and it’s a way for fans to keep up with their favorite celebrities.

Recently, Lance Armstrong sent out a tweet that he was going to a ride around the LA Zoo. When the seven-time Tour de France winner arrived, hundreds of bikers were ready to join him.

With some estimating more than 45 million monthly visitors for the social website, Twitter can also be used as a powerful marketing tool. Dave Hollander adjunct professor for NYU School of Sports Management feels some athletes are using Twitter the right way.

“Shaq is a master of Twitter,” said Hollander. “We all know that it’s a publicist behind Shaq sometimes, but the way Shaq does it, it doesn’t matter. To Shaquille O’Neal its just free marketing. He is the highest ranked sports figure with more than 2.1 million Twitter followers.”

On the other hand, some athletes seem to find ways to get in trouble with the social networking website. Former Milwaukee Bucks forward Charlie Villanueva was in hot water for tweeting during halftime of a game against Boston. Chargers cornerback Antonio Cromartie was fined $2,500 by the team for tweeting a complaint about the team’s food at Chargers Park. Bengal’s wide receiver Chad Ochocinco consistently challenges the NFL regarding its rules on social networks.

The league’s official rule says NFL players and coaches can only post 90 minutes before kickoff. The ban is lifted once the scoreboard is in the record books. OchoCinco sought to enlist a “follower” of his on Twitter to tweet for him during a game. The league also added a rule banning representative tweeting for a player and coach.

Hollander says ownership is the big issue. “They’re an employee of the NFL. We handle information that’s not ours, it is in our custody temporarily while we are employed and we have agency to share it but we don’t have unfretted permission. We don’t own it, “he said.

Twitter is changing the way sports news is broken. NBA guard Allen Iverson has bypassed mainstream media outlets and informed his fans directly that he was going to join the Memphis Grizzlies. Some news organizations have been reporting on his tweets, which raised questions about authenticity.

The Boston Herald reported the Celtics forward Glen Davis used his Twitter account to vent about his lack of a contract with the team. Later Davis said he did not post that tweet and it was from a fake account.

With all of these issues some have asked if athletes should tweet at all? Hollander says yes but they should proceed with caution.

“If you don’t have talent for it hire someone who does, and if you cant hire someone don’t do it. It’s a loaded gun in the hands of someone that doesn’t know what they are doing,” he said.