Google spoke about their Google Now tech and it's capabilities in Android 4.1 Jelly Bean at the day 1 Google IO 2012 keynote today.

It sounds awesome in its ability to tap into everything Google knows about you to present you information about your schedule and surroundings before you even ask for it. However... its strength is also the largest point of concern. It leverages all the info Google has collected about you. It works best if Google knows more about you than you do. Its effectiveness depends on centralized, privacy intrusive knowledge.

Many users are going to be oblivious to the amount of privacy they surrender to Google in order to power these services. If they knew, I don't think they'd be happy about it. Depending on the ignorance of users as a business plan is a questionable practice and will eventually come back to bite them -- think, Congressional inquiries.

Ideally, I would prefer a decentralized approach to a service like Google Now. My personal information should be distributed across services that vend that information to client apps I give permission to. So, one company may have my calendar information, another my travel plans, a third my social info, etc. An aggregating client app can do what Google Now does by pulling my info from those various sources to create an aggregate view that no single data service can provide alone. Distributing my information across many sources makes my information more private (through the prevention of aggregation) but still allows that information to be aggregated locally by special purpose software. The key is that aggregation happens locally, under my control, not without my knowledge on the servers of a company that looks to profit off that information whether I allow it or not.