I'll give you another thought to chew on. Everyone is focusing on the 'spying' aspect to catch you in what you are saying or believe. There is another thing to look at. I actually have some experience with this partnering with a company called Acxiom years ago. Data mining can optimize predictive marketing.
Instead of 'punishing' wrong-think, control thinking through very predictive and targeted marketing campaigns.
I will dig up my notes and post more about this but to give you something that will make you think, I saw a video demonstration at the aforementioned company of a test a marketing company did with them to show the power of predictive, subliminal marketing. They used the Times Square video billboard as the delivery method and had a demonstration on how they increased orange juice sales at the McDonalds in Times Square over 400% in a one hour period simply by putting in some suggestions in a completely unrelated commercial on the video screen a half block away. It was a combinations of slight color changes, a few words thrown in some sports commercial I think (can't remember the details, just the results). They played the commercial then had a live sales graph going for the next hour. In the middle of the afternoon, when they may sell a couple of OJs, if any at all, person after person walked in asking for one.
Imagine what these type of experts could do on a national, political level with any issue with the amount of data we are talking about.