Microsoft admitted European privacy laws and has claimed that they will make some changes in Bing, an Internet searching engine, by discarding user data. Read more
Google as an Internet integrator and a powerful search engine all in one, has now plenty of private information: Gmail- personal correspondence + GTalk, GoogleDocs (for legal entities- perhaps confidential), Calendar, Travel, Youtube, Shopping, Maps, Books, etc. Google identifies a user in all its services. So in fact, they already know a lot about you and who guarantees that do not collect information that can be analyzed.
The question is not only about Would you trust Google (Bing, Yahoo, etc)? . Companies using now Google’s services are subject to the following main risks: leakage of secret data, loss of copyright, destruction of information. One main concern here is Who except you has access to your data and under what circumstances? For sure, Google’s employees have access to your unencrypted files, and to develop its (Google’s) context advertising will have to start indexing these data. Indeed, to get an access to those data might be taken by authority, business institutions, and even hackers.