TPI has published the paper has some privacy groups and U.S. lawmakers have called for more regulations on online advertising. Representative Rick Boucher, a Virginia Democrat, has promised in recent weeks to push for legislation that would limit how Internet service providers can track their users.

Earlier this month, new U.S. Federal Trade Commission Chairman Jon Leibowitz said he believes ISPs and Web sites tracking user behavior should get opt-in permission before doing so. The FTC will look at filing cases against Internet firms that don't give adequate notice and consent before tracking customers or altering privacy policies, Leibowitz said on C-SPAN's television program.

"I think the better practice is always opt in," Leibowitz said. "Then consumers ... think about what they're doing rather than just clicking a box."

In many cases, Web sites tracking user behavior now require their customers to opt out of the data collection. If Web sites must get opt-in approval, the majority of customers would likely not participate and the online advertising model will break down, Lenard said.

"The evidence thus far is that consumers by and large stay with the default and opt-in rates would be very low, even if at some level consumers recognize the benefits," he added. "My concern is that this could be quite costly to consumers in terms of diminished revenues to support services, less-well-targeted advertising, and that it would make it more difficult for entrepreneurs to develop new online business models that would benefit consumers."