I don’t actually use the twitter backchannel with Textmark and TexttheMob. Textmarks and Textthemob are backchannels unto themselves.I use those two services when the people in the audience are not already Twitter users and I don’t have the time in the session to set them all up on twitter.

I monitor Twitter hashtags with http://www.tweetgrid.com (I put it up in the corner of the projection screen) and Textmarks/Textthemob gives you an easily updatable webpage to check for the backchannel.

Generally, I use a backchannel for two reasions:

1. A collaborative note taking space
2. A place to ask and answer questions

Let me know if I should do a large post on backchanneling and I will.