One of the newest Web 2.0 tools that has really taken off in the libraries is Chat. Ask Us 24/7, is the one my library system uses. I have previously discussed this topic in this blog when I personally gave it a try.
Last night, my group met to discuss our project. Interestingly enough, Google chat kicked two out of three of us off of the site, with no warning. It did not let us log back in either. So we switched to Skype.
I think it is important for these tools to be monitored carefully. Especially when there are so many alternatives. If one does not work, users will just use another one.