Well..
They are a load of shite.
The Mountain View Chocolate Factory has unveiled an extensions gallery for Google Wave, the still-gestating browser-based app that crossbreeds email with IM and document sharing. First unveiled at a Google developer conference last May, Wave offers APIs for developing extensions to the platform and embedding its conversations …
... and I'm thoroughly underwhelmed. About the best use I can see is as a collaboration environment for a small, geographically diverse team. I think of it as a cross between pastebucket and a twitter stream. Something may come out of this experiment eventually, and I'm sure people will find uses for it, but I don't see it going mainstream until Google binds it inas an inescapable part of gmail... ;-)