Google has already admitted it did an end run around privacy settings on Apple's Safari Web browser so it could use a "+1" button on some of its ads that would allow a user to spread the word among friends that the ad was helpful, The Wall Street Journal reported Saturday.
Google said the system inadvertently allowed it to plant digital markers called cookies onto computers that would allow the company to track a user's online activities.
The system planted cookies on iPhones, iPads and personal computers.
Google, however, could be facing steep fines for cookies that circumvented firewalls set in place to prevent the cookies from establishing themselves on computers and other devices.
In particular, Google in 2011 signed an agreement with the Federal Trade Commission in which it said it would not "misrepresent" its own privacy rules.
Google would be in violation of that agreement if regulators could prove Google willfully "misrepresented" its privacy agreement. If a violation is ruled inadvertent, Google would be off the hook.
"We will, of course, cooperate with any officials who have questions. But it's important to remember that we didn't anticipate this would happen and we have been removing these advertising cookies from Safari browsers."
Tracking the response of users to advertising can provide a snowball effect for revenues. If Internet firms are aware of the specific likes and dislikes of individual consumers, it can sell advertising that targets a select customer group -- mothers of newborns, for example.
The more selectively an Internet firm can target advertisements, the higher the price it can demand for those advertisements.