Most of the Twitter messages go like this:

"Just got my google wave invitation"
"Is still waiting for my google wave invite"

An interesting message:

"Google Wave is trending topic again. Means GOOG has pumped out a LOT more invites, desperate for self-sustaining network effects?"

twitter.com/hc/statuses/570841 ...

Another interesting message:

"Google has also announced that if Google Wave trends on Twitter for 72 hours they'll invite 72k more people."

twitter.com/bacardimo/statuses ...

I can't find the source.