Calling someone a "jerk" and a "buffoon" may be safe from a lawsuit because it states an opinion. Saying he wrongly "pocketed" public money could lead to a defamation claim because it asserts something as a fact.

And it's not hard to track down anonymous commenters:

A lot of people don't know how easy it is to track them down" once a lawsuit is filed, said Sara J. Rose, an American Civil Liberties Union lawyer in Pittsburgh.

In one lawsuit last month, the 9th Circuit upheld a trial court's order requiring disclosure of three posters who engaged in a smear campaign against a company.

"The right to speak, whether anonymously or otherwise, is not unlimited," wrote Judge Margaret McKeown."

Advice from the media law experts:

The first thing people need to realize, they can be held accountable for what they say online," Baron said. "Before you speak ill of anyone online, you should think hard before pressing the 'send' button."

In other words, remember that the internet has no eraser.