What if I don't trust the green address provider?
Then don't run this particular client software.
Green address should be an optional service and if you use it is between you and the provider.
Exactly:
Option 1) use regular bitcoin software which uses the full blockchain
Option 2) use modified bitcoin software which uses a published list of green addresses and cuts down blockchain
Anyway, the other replies have shown me that it's not needed / not going to work anyway.
Just a thought.