The change comes on the heels of an FCC inquiry into out-of-control termination fees. Up until now, Nexus One owners were expected to pay $350 in the event of canceling or downgrading their T-Mobile contracts within 120 days. With the new Terms of Sale, however:
"You agree to pay Google an equipment subsidy recovery fee (the "Equipment Recovery Fee") in the event you cancel or downgrade your wireless plan within 120 days of activation of wireless service. If you activate a new line of service with T-Mobile, your Equipment Recovery Fee will be $150 USD if you cancel or downgrade your service plan within 120 days of activation."
Obviously, Google doesn't want folks selling phones under contract for profit, and they claim not to make any money off of equipment recovery. But while $150 extra is better than $350 extra, it's still a huge fine to impose on someone for changing their mind. [Google Terms of Sale via WSJ]