> You cannot prevent that some entity will have private data about you, once you start using mainstream online services whose focus is on mainstream issues like ease of use, portability of data and seamless access from multiple devices.
You could encrypt the data locally before sending it to the server. You might also question whether this model of computing is in fact sensible. There are at least partial alternatives, for instance holding all data locally on a smartphone, and then plugging that in to use as a desktop, tablet etc. We should be asking whether the advantages of the Google model outweigh its (significant) disadvantages.
In fact it would probably be a good idea for Google to proactively report/describe some of the technical tradeoffs they have made when it is related to privacy.
Because what most people do is judge based on incomplete information - and Google has more and more problems with its public perception.
Regarding the idea of encrypting all data (I believe you mean that not even Google should be able to decrypt it) before sending it to the servers I see some issues, but my views on cryptography are probably pretty naive.
1) There are laws that force them to hand over data to governments when courts order it - I do not know if they would get away with only turning over encrypted data.
2) They also have business goals - like increasing ad revenue by matching ads to the personal preferences of its users.
3) They have social interactions in most of their products - I don't know how this could work with total encryption.
4) There are certainly some usability tradeoffs to make - like how many times does a user have to enter a password to access his data.
You could encrypt the data locally before sending it to the server. You might also question whether this model of computing is in fact sensible. There are at least partial alternatives, for instance holding all data locally on a smartphone, and then plugging that in to use as a desktop, tablet etc. We should be asking whether the advantages of the Google model outweigh its (significant) disadvantages.