Google Wave clutter
Today I started to experience the first thing that I could point to in my current Wave usage that is an actual pain to deal with – the ability for anyone to add you to a wave. The inbox is now starting to regularly have waves with 400+ participants that I never looked at or was invited to by a contact. When you archive them they will just come back on the next update and when you mute them, your unread counter in the title bar will still reflect them.
So hopefully that is a feature high on the dev teams todo list.