Look at a Twitter search for @LeoLaporte to see all the people responding to him and/or trying to engage with him, or look at his Twitter stream to see him interacting with people himself. For that matter, look at all of the people commenting on his Buzz postings directly (e.g. http://www.google.com/buzz/laporte/iGbULnn1UMH/Its-funny-bec...)

None of that squares very well with the echo chamber claim.