I think too much of the culture of "web 2.0" is skewed or geared towards mash-ups. There is so much love at places like google to invent something that someone else can do something with it. Map with traffic overlay, real-time chat with a translator bot, etc.
Wave in trying to be all things to all people overdid it and wasn't even ready. It is kind of the same with twitter, still getting the whale over capacity thing and being slower than molasses sometimes.
Offer something to people and roll the dice that people will get it, like it and tolerate its short comings.