Tag-It! Tag-It! Tag-It!
Besides the already mentioned advantages of tagging systems, which are ease of use and simplicity, the latter is also a critique point: In some cases it is too simple and the semantic of a tag is not always perfectly clear. In our problem domain these cases are rare and if you hit a tag like "Eiffel" and you don't know whether it's the tower in Paris or not, be sure that it's most likely something related to computer science ;-)
The other drawback is the use of synonyms or slightly different spellings for the same word. To tackle this issue we have auto completion to support the emergence of the eiffelroom vocabulary. In order to have an accurate search nonetheless we're able to explicitly state which tags are synonyms.
By knowing the issues of the system, we're able to pay attention and to avoid them wherever possible to increase consistency, the accuracy of the search and the overall experience.
So let's tag and enjoy the evolving tag bubble on the front page of the eiffelroom.