Checkout Google's motives
The service is free? Wonderful! This just shows that Google really is our friend, looking out for our interests, and they're not just out for profit like every other corporation. I think the low fees that they charge on Google Checkout also confirm this viewpoint.
Er, what's that? The fee structure for Google Checkout was just a bait and switch scam, and now they've got some customers they've raised the fees to be just as bad as PayPal?
Oh well, I'm sure that'll never happen with Google Voice. It's not like they're going to wait until you have a Google telephone number, and given it out to all of your contacts, before suddenly noticing they're losing money and they have to introduce a "small fee" for the service.
I'll sign up right now.