Of course this would be an extremely valuable service for Google, but medical industry is very powerful and clouded by federal laws. As we move forward, electronic health records are still right around the corner and someone will make all the money. I doubt there will be more then one private entity storing your data, but then again it could be like Medicare D and you have to choose from 20+ companies.
(By the way, the presentation on Google Health was the best and most professional presentation I've ever seen. They hire pros for real.)