Second issue they had was scalability of the service and I suspect the invite system was probably implemented to give them time to scale it.

On some large subjects with many people contributing the service was practically unusable.

... made even more absurd by the fact that it is a collaboration platform. I actually at the time collaborated on some large, complex documents, but the people I did it with weren't on Wave.

In an alternate universe:

I think where Google messed up was letting everyone try it on day one.

Pretty hard to get on board when day one is just laggy and chaotic. Performance--;

It could have been so big and awesome. I'm sure after a while the speed issues would have been ironed out.