Yes, it IS possible to live in an echo chamber when you depend on blogs for your information. Diversity of sources is key. Case in point, many of the conservative blogs are reporting that $150K of Oil For Food money has been found in George Galloway's wife's bank account. What do we find on liberal blogs? A refutation? A contrary opinion?
How about not a damned thing? That's right. Such a thing is completely absent from the liberal blogs I read. Which is why it's important to realize the bias inherent in one's sources and try to balance it out with some contrary opinions and biases. From the marketplace of ideas will rise the truth, but only if the marketplace is a true marketplace.