The sad thing here is that Google did the polite thing, and turned off email notifications by default. It actually took some searching to figure out how to turn it on.

Contrast this with Buzz, where they dropped it right in the middle of your inbox. Quite the opposite strategy.

I suppose the solution I favor is to ask the user if they want notifications when they sign up. Or at the very least making it very obvious how to turn on notifications if you want them.

The notification messages were also not very well thought out, it was often confusing what had changed, requiring you to log in to Wave just to read a new message that could have easily been read via email.