EIFFEL_ROOM is a pretty big room and has plenty of space available for all kind of things, a neat way to have some kind of order has to be available. The ultimate goal is to be able to keep total chaos on a reasonable distance without spending to much effort in doing so.
In order to have some kind of categorization system we decided to use the now widely spread and well known concept of a so called "tag system". Actually you'll find them at a lot of other places. Among the first, now well known sites are flickr, del.icio.us, last.fm and others.
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.