BlogRolls become echo-chambers when people who agree spend all their time reading and agree-ing with each other. An echo-chamber is a hermetic community who tend to develop and re-enforce a view point because they don't get enough alternative views from outside.
- More anti-blog scepticism from AndrewOrlowsky : (and http://www.theregister.co.uk/2005/01/05/pew_pajamahadeen/ (and with an interesting note that popular political blog DailyKos changed from blog format to SlashDot style DiscussionForum software.)
- CriticalRationalism is deliberately seeking out those who disagree and may be able to help correct your errors.
- PersonalKnowledgeManagement when it's good to have a bit of an echo-chamber