Metcalf's law indicates that value of a communications technology is proportional to the size, or perhaps more importantly the percentage penetration of that media ... I might add within a critical community. I understand that one of the first phone systems was installed at the Shaker Colony in Canterbury New Hampshire ... they wanted to avoid the need to travel from building to building to communicate with each other. That probably got good use, given 100% penetration within a critical community.
Google Wave, as far as I can tell, is currently constrained by it's 'invitation' bottle neck. Only primary invitees can invite others (I'm second tier, so I can't initiate invites) ... and if you can't connect your waves with others, then things don't reach critical mass and take off. Of course if Google opens the flood gates, then their resources could be overwhelmed by either success, or any significant bugs.
When I encountered a wave Bug recently, I found there was no real way to report it (you can post it in an online community that apparently some Google folks track, but there is no "here's a bug" reporting and tracking system apparent.)
Good news: we do have a preliminary IEEE dialog started in Wave ... but only three of use actually have accounts (sigh)