Because state laws vary in scope, many suits are still filed every year, according to legal experts. Now, with people musing publicly online and businesses feeling defenseless against these critics, the debate over the suits is shifting to the Web.

“We are beyond the low-tech era of people getting Slapped because of letters they wrote to politicians or testimony they gave at a City Council meeting,” said George W. Pring, a University of Denver law professor who co-wrote the 1996 book “Slapps: Getting Sued For Speaking Out.”

Marc Randazza, a First Amendment lawyer who has defended clients against suits stemming from online comments, said he helped one client, Thomas Alascio, avoid a lawsuit last year after he posted negative remarks about a Florida car dealership on his Twitter account.

“There is not a worse dealership on the planet,” read one post, which also named the dealership.

The dealership threatened to sue Mr. Alascio if he did not remove the posts. Mr. Randazza responded in a letter that although Mr. Alascio admitted that the dealership might not be the worst in the world, his comments constituted protected speech because they were his opinion.

While the dealership did not sue, that outcome is unusual, said Mr. Randazza, who conceded that sometimes the most pragmatic approach for a Slapp defendant is to take back the offending comments in lieu of a lawsuit.

In the past, Mr. Randazza said, if you criticized a business while standing around in a bar, it went “no further than the sound of your voice.”

Now, however, “there’s a potentially permanent record of it as soon as you hit ‘publish’ on the computer,” he said. “It goes global within minutes.”