Microsoft and Google are among those who have received letters from four members of the House Energy and Commerce Committee expressing concerns over their online advertising methodologies.

The letter asks the companies to respond by Friday to eleven questions revolving around the subject of targeting ads to specific users, based on behavior or other disseminated factors. The congressmen are looking for answers as to how the companies engage in the practice and to what extent, as well as with regard to address privacy and legal concerns.

"As you may know, questions have been raised regarding the applicability of privacy protections...to such practices, and whether legislation is needed to ensure that the same protections apply regardless of the particular technologies or companies involved," the letter reads (PDF available here).

It is signed by Commerce Committee Chair Rep. John Dingell (D - Mich.), ranking member Joe Barton (R - Texas), as well as Telecommunications and the Internet Subcommittee Chair Rep. Edward Markey (D - Mass.), and ranking member Cliff Stearns (R - Fla.).

"Privacy is a cornerstone of freedom. Online users have a right to explicitly know when their broadband provider is tracking their activity and collecting potentially sensitive and personal information," Markey said in a statement.

Other than Microsoft and Google, AOL and Yahoo were sent letters. In addition, cable companies were sent notices including Bright House, Cox, Comcast, and Time Warner, and telecommunications companies were not immune: AT&T, Qwest, and Verizon were also targeted.

Congress voted last week to adjourn for the summer recess, ironically one week after it had moved up its original vote for adjournment by one week.