Click on the title and you'll hear and watch John Udell walk you through using "delicious". It's a lucid exposition of how tags and tagging contribute to language evolution. Tagging, as Bernard suggests in his previous univers immedia post here, appears to have great merit. John Udell's page ends with a thoughtful commentary on the relationship between tagging and Steven Pinker's writings on language.
Consider this: language is the longest-running open source project on this planet.