Well, even though many if not most of my friends ended up with an invite (and we made active use of Wave), that didn't make it a success: the client was just too slow and laggy. It basically only worked in chrome, and poorly there. Large threads were simply unusable.

I don't think the closed beta-ness of wave really hurt it. If wave had actually worked well, then maybe there'd have been a point where it was worth opening up to many users - but wave never got there, so it's a moot point.