If user data is the lifeblood of interactive advertising, it seems there will be less of it to go around now that Google has said it will no longer store information for 18 months.

Google made the decision to halve the duration of data storage amid growing concerns raised by privacy advocates.

"We're significantly shortening our previous 18-month retention policy to address regulatory concerns and to take another step to improve privacy for our users," Google officials said in a blog post released Monday night.

While it's not clear how the policy change will affect ad targeting, Google did say that the data restriction would hamper innovation. However, Google may have had little choice in its decision, given the Justice Department's recent decision to put its proposed search deal with Yahoo under the microscope.