I agree with the California Supreme Court on this one. The police can "knock and talk" with someone -- i.e., can knock on their door and converse with them, including asking for consent to search the home -- without much constitutional scrutiny; e.g., pursuant to an anonymous, unconfirmed tip. You always have the right to tell the police "No, you can't come in unless you have a warrant." And as long as that's clear, I don't see the harm in letting the police knock on your door and see if you want to voluntarily assist them.
Makes sense to me.