When the US Federal Trade Commission announced a US$2.9 million settlement with online marketing firm ValueClick this month, it was a record monetary settlement under the 4-year-old CAN-SPAM Act.

That announcement came just days after so-called spam king Robert Soloway pleaded guilty in the US to a number of criminal charges. Soloway, who faced one count related to CAN-SPAM in addition to mail fraud, wire fraud and other charges, faces up to 26 years in prison.

But despite these recent court cases, some critics don't see a lot of value in CAN-SPAM, short for Controlling the Assault of Non-Solicited Pornography and Marketing.

"CAN-SPAM has had virtually no impact on the spam problem at large," said Ray Everett-Church, a longtime spam fighter and director of policy and professional services at Habeas, a company that provides e-mail authentication services. "It has enabled the FTC to take action against a few bad actors, and that has worked to deter some otherwise legitimate companies from playing fast and loose with the rules."

But spam is as big of a problem as ever, and the worst spammers "remain unfazed and undeterred" by CAN-SPAM, Everett-Church said. Everett-Church and other antispam activists criticize CAN-SPAM for allowing marketers to send unsolicited commercial e-mail until people opt out.

Harvard University technology security officer Scott Bradner called spam prosecutions and settlements "all too rare". "To say that the FTC has been careful in its approach to enforcing this act would be misleading -- a better word would be 'lethargic' or maybe 'comatose,'" he wrote.

Officials with the FTC and the US Department of Justice say criminal spam cases can be difficult to investigate because spammers often hide their identities through falsified e-mail headers, offshore servers, and affiliate senders and payment processors. Still, the DOJ has prosecuted about a dozen criminal spam cases in the past four years, and the FTC has taken civil action in 31 CAN-SPAM cases, according to officials at both agencies.

Including cases before CAN-SPAM passed, the FTC has taken action in more than 90 spam cases, involving more than 250 defendants. In addition, CAN-SPAM allows state attorneys general to file lawsuits against spammers, and several have done so.

At the DOJ, CAN-SPAM has helped prosecutors build cases against spammers, and in some cases, the spam charges have led to other charges, DOJ officials said.

Among the cases: The DOJ in January indicted 11 people, including alleged master spammer Alan Ralsky, accusing them of using a sophisticated and extensive spamming operation that fueled a stock pump-and-dump scheme. The defendants allegedly used spam to tout Chinese penny stocks, driving up the price of the stock and selling it at artificially inflated prices, according to the DOJ.

In June 2007, a federal jury in Phoenix convicted two US men on charges of conspiracy, fraud, money laundering and transportation of obscene materials, in a case in which the defendants were accused of sending pornographic images in millions of pieces of unwanted e-mail. The case, which began as a CAN-SPAM investigation, escalated to include other charges, and the DOJ found that children had received some of the "hardcore" e-mails, a DOJ official said.