Senate hearings taking place this week will cover online privacy concerns and feature representatives from several prominent Internet companies, including Facebook, Google, Microsoft and others.

One company receiving some specific focus is the startup NebuAd, a company that helps contextual advertisers track Internet behavior of users online. The company has been criticized by privacy advocates concerned that this type of tracking goes too far.

The hearing may also zero in on Facebook's controversial "Beacon" tool, which the site made a strictly "opt in" service after its launch last fall sparked privacy concerns among users.