Could be a good time to be not yet in print
There might be no better time to stay out of print than now, while your as-yet-unpublished book isn't covered by the agreement. Published writers, you and your publisher have until June, 2010 to file an objection to the agreement if Google has already scanned your book. Nobody has seen the latest version of the agreement promised today. But DC Comics and Microsoft have filed objections to the existing settlement.
The Authors Guild threw up a roadblock to Google's scan-and-display policy when it was announced last year. A fairness hearing in US, scheduled for today, has been delayed until next month.
The Guild is the domain of the published writer, and the organization takes its eligibility to an exclusive level. Even if you have a book contract, it must "include a royalty clause and a significant advance, and must allow the author to retain copyright." Independent book publishers, who are accepting new books from new authors at a faster rate than major presses, are skipping advances these days. The Guild accepts members whose books are "published by an established American publisher... excepting small literary presses of national reputation."
So whatever agreement the Guild, major publishers and Google arrive at, it won't keep you from disputing when Google scans your small-press book and charges to read it. With exclusive eligibility requirements like these, Google is just ensuring that those left out of the agreement will probably welcome the online readership as a way to promote the books -- which will likely have links to online stores. That's where Google makes its money anyway, not in the per-reader charges.