It had been invite-only for most of its life and only opened to the general public for something like a month or less before its shutdown. It would have been dumb for Google to shut it down on "lack of usage" if their own artificial barriers were the reason for such.
Lack of usage is getting a lot of blame in these threads, but let's not forget it was most likely a Google+ related strategic decision. Wave was built with an XMPP-like or email-like federation model in mind and was shutdown in basically the exact same cohort with XMPP-based Google Talk and RSS-based Google Reader. Google was strategically no longer interested in standards-based (or standards-aspiring perhaps in the case of Wave) social networks.
This makes me wonder how much different things would be if Google had doubled downed on an Open Social (tm) model instead of trying to me-too Facebook et. al. by building a walled garden (more like a walled dirt lot I guess)
Lack of usage is getting a lot of blame in these threads, but let's not forget it was most likely a Google+ related strategic decision. Wave was built with an XMPP-like or email-like federation model in mind and was shutdown in basically the exact same cohort with XMPP-based Google Talk and RSS-based Google Reader. Google was strategically no longer interested in standards-based (or standards-aspiring perhaps in the case of Wave) social networks.