When the New York State Legislature drafted a privacy law 100 years ago, Facebook and online advertising didn't exist. But now the law, the social network and the ads that help the web darling monetize its traffic, are on a collision course, according to a law professor.

William McGeveran, a professor at the University of Minnesota Law School, wrote in a blog post, that Facebook's new ad program violates New York's privacy law and opens the company up to lawsuits from users and criminal liability.

The program, which attaches ads to the names and pictures of Facebook users, violates the law, according to McGeveran because the Facebook does not have prior written consent from its members to use their names and likeness for commercial purposes.

To compound matters, McGeveran also said that advertisers who use Facebook's new program could also open themselves and their brands up to lawsuits from Facebook users. But as McGeveran points out, users might not be too keen to sue Facebook.

"It's unclear that today's teenagers and twentysomethings will be too upset by this," McGeveran said.

Whether New York prosecutors would take action for a misdemeanor also seems unlikely. However, Facebook and MySpace have come under fire from various state attorneys general, including New York's, for not doing enough to protect minors. According to McGeveran, the new ad program gives New York additional leverage in dealing with Facebook.

For its part, Facebook disputes McGeveran's assertions.

Chris Kelly, the chief privacy officer of Facebook, told The New York Times that McGeveran's interpretation of the law is too broad.

"We are fairly confident that our operation is well presented to users and that they can make their own choices about whether they want to affiliate with brands that put up Facebook pages," Kelly said.