I had an interesting brief chat this morning at eDemocracyCamp with Peter Corbett. We were talking about the power of hashtags.
Most people don’t yet understand that hashtags are an extremely strategic, powerful and valuable way to inform targeted communities about related concepts, events and topics.
For example, if I am attending eDemocracyCamp and hear or share something that may also be a valuable insight to those currently attending FooCamp, I can co-tag my “#edemcamp” tweet with “#foocamp” to share my comment with Foo Camp attendees. This not only exposes another entire community to this information nugget, but potentially catalyzes discussion around this topic within that community. This type of cross-pollination can yield unique and innovative solutions because it infuses a discussion with input from a tangentially-related community who have different assumptions, education and perspectives.
This also, however, brings up the interesting line between using hashtags for good and not for evil. There is a fine line between informing and marketing. Misuse of the power of hashtags = spam. Informing and enlightening with hashtags is valuable. Marketing with hashtags dilutes their value.

Maxine, you make a great point about hashtags being an ideal way to catalog tweets and brings events and topics to the attention of your followers. There are two drawbacks to hashtags, however:
1) They don’t always make sense. For this, a simple remedy is simply to create an entry at http://tagal.us/.
2) They eat away at your character count. No remedy for this except to keep them short.
Thanks for the reminder!
Glad you are pointing this out, Maxine. Using Twitter without hashtags is like wearing a blindfold. You should definitely check out @jdp23 and @shoq, both very interested in the semantic Web.
Like the cross pollination term. I think hashtags are becoming more and more important in the use of Twitter for actual marketing and for businesses to use them as a free tool.
And all conferences should have a hashtag – in fact any gathering of people should have one to be honest as it is a great tool for networking before during and afterwards.