I've made some small changes based on great input from my friend Robert Brewer (and George Lee and Ken Mayer), such as making each icon have a minimum size so you have a fighting chance of seeing who of your twitter friends is not being very active. A little more cleaning up and I hope to release this to anyone who wants to see their own twitter friends activity cloud.
Last stumbling block is that getting all the data requires hitting twitter as many times as you have friends, and if this exceeds the 100 requests per hour that twitter allows then the interface can fail a little ungracefully. Hope to fix that and do at least a partial release next week. Hoping to get my twitter friends to test it first, and then all comers, gulp!