Google wants MORE information from you? I hate to break it to you but unless you have your "do not track" setting turned on, Google already knows more about you than your Mom does. Giving them more information is only going to make your experience when surfing that much better. They already know what you search for and send you ads pertinent to that info. They know where you bank, what kind of credit cards you have and what time you go to the bathroom in the morning. Well, maybe not the last one. But anyway, they already have most of your info so giving them a little more isn't going to hurt.
I don't think they need too much personal information, but it really depends on what you are using the system for. If you need it for extensive use, then it might be a good idea to have more information provided to get more accurate assistance. If you just use it occasionally, then no.
It is sad that we live in a world where people have chosen to sacrifice their personal freedoms, i.e. privacy and security for minor added shopping convenience. Unfortunately, as the ignorant masses through away their own freedoms, they fail to respect the privacy rights of others and allow the trampling on all peoples privacy rights. Google, Facebook and many other companies are in gross violation of our rights, unfortunately our dumbed down society will never hold them accountable.
Google is insane to think people will provide more personal information to them. The need for an online personal assistant is in my opinion a sneaky way to collect data from it's users. If you are in that desperate of a need for a personal assistant, them hire one. This way you know your information is kept safe.