It boils down to the conditions you agree to when signing up. They are quite broad and Google reserves lot of rights to a lot. Here is en enlaged version of the text at the bottom of the sign-up page for individuals, my highlighting:
By selecting "I agree", you agree that Google may use, adapt, translate, and copy your submission materials to advertise, publicize, and promote Google's business activities in present or future media. You agree that Google may incorporate its own audio, visual, musical, and other effects into such materials. (...)
Google reserves the right to contact you about Chrome OS or related Google products by email, phone, post, or in-person upon submitting this application. Please indicate your agreement to the above terms by clicking "I agree".
As you can see this is not just a beta-test where you supply Google with voluntary information and problems with the device. They can use your information (probably including your name) in advertisements and publications without your specific later consent. They may mix your information with other information. You must let them take statistics about your browsing.
And you must allow to come and contact you, even in person at your home address and probably even without prior notification. Just reading the text it seems that even if you're not signed up to the program, they could put your name, phone number, email and address in an advertisement about Chrome OS including the pages you visit frequently.
I mean, I'm not a lawyer, but this doesn't look to me like it's worth a netbook still in its development stage.
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