Google expects to keep Wave as a developer preview product for at least several more months. For starters, only developers attending I/O will get access to Wave on Thursday. Google will expand access to more developers later.

Rasmussen warns that the Wave code will appear rough even to developers, so those interested should be of the adventurous type who like to be early adopters and participate in the evolution of a product.

While Wave doesn't inherently have a "friends graph" function, Google expects developers will build integration links for it with social-networking sites. During the keynote, the Wave team will show an early integration with Twitter.