Twitter-tags (or hashtags), what do they mean?

When starting to use Twitter, you often see a lot of Tweets that contain acronyms starting with a "#".
These are called hashtags ... this site allows users to explain their meaning.
Anybody can define his own hashtag, and as such, this site becomes a dictionary of hashtags.

The nifty thing about these hashtags is that:
1/ they are short (remember, Twitter only allows for 140 characters in a single message),
2/ they are easily searchable (check the Twitter search engine, that allows you to "save" your search as an RSS feed ... nice): if you want to keep track of Tweets about knowledge management, want do you need to search for ? "KM", or "knowledge management", or still some other name? No, just search for "#KM", the hashtag generally used to "tag" Tweets about knowledge management.

Arnold.