Today was my first Skypecast and I can see that it might be quite difficult to do with a large group.
Even with a quite knowledgable group, the technology was sketchy at best. It took 30 minutes to get going and even then there were many individuals who were either having troubles with their technology or simply didn’t know how to participate properly (i.e., muting mics, moving to the “listening” section, etc.).
However, once it got going, it was great. This is a wonderful way to conference. While Skype 3.0 allows conference calls, these have to be know entities (in your contacts), while the Skypecast opens it up to larger (possibly nameless/faceless) people.