Congress is trying to wrap its collective head around Amazon's new Silk Web browser.

At a privacy hearing yesterday, Rep. Joe Barton (R-TX) expressed outrage at the way Silk's "split" design can funnel all user browsing data through Amazon's backend servers.

"My staff yesterday told me that one of our leading Internet companies, Amazon, is going to create their own server and their own system and they're going to force everybody that uses Amazon to go through their server and they're going to collect all this information on each person who does that without that person's knowledge. Enough is enough."

Today came a similar shot from the other side of the aisle, with Rep. Ed Markey (D-MA) dashing off a letter (PDF) to Amazon CEO Jeff Bezos about the same privacy concerns.

“Consumers may buy the new Kindle Fire to read ‘1984,’ but they may not realize that the tablet’s ‘Big Browser’ may be watching their every keystroke when they are online,” Markey said in a statement. “As the use of mobile devices, especially tablets, becomes ubiquitous, we must ensure that user privacy is protected and proper safeguards are in place so that consumers know if and when their personal information is being used and for what purpose."

To that end, Markey has some questions for Amazon. As the co-Chair of the Congressional Bi-Partisan Privacy Caucus, Markey wants to know in the next few weeks:

What information does Amazon plan to collect about users of the Kindle Fire?

How does Amazon intend to use this information?

How will Amazon convey its privacy policy to Fire and Silk users?

If Amazon plans to collect information about its users' Internet browsing habits, will customers be able to affirmatively opt in to participate in the data sharing program?

Good questions, all, though Amazon has already provided partial answers. The company told us at the Kindle Fire launch that Silk will collect and retain user data, but only in anonymized and bundled form. In addition, users can switch off the backend Amazon processing and run Silk as a normal Web browser, where traffic does not pass through Amazon's servers. But Silk's "split" operation appears to be the default (Amazon says it makes browsing on the Fire much speedier), and the amount of information Amazon could have access to is staggering.