I was reading some articles in Time Magazine on the flight from Seattle to San Jose about the American Elections, it's amazing to see how both sides are using technology to build monster databases that provide intelligence on potential voters, this includes personal data including home address, phone numbers, birthdays, this gets cross referenced with census data, plus any additional data the party can pull together (perhaps credit history etc...) - each record can contain up-to 400 pieces of information on an individual.
So how private is your private life, your position can be tracked through your cell phone location (see the location based server video on MSDN Channel 9 - or Steve Lombardi's current cell phone location), your movements throughout the day can be tracked based on purchases you make on your credit/debit card - banks can determine (through AI systems) whether you are stepping out of your normal spending pattern, this raises a red flag so the bank can potentially put your card on hold (this happened to me when I took a day trip from Mt Baker to Vancouver). Companies like Amazon and others track your online spending so they can recommend other items that might appeal to you (based on similar purchases other people make).
Your ISP can track the web pages you visit, your corporate IT group can do the same - Stores, gas stations, shopping malls, and other public places have a ton of cameras which can track you throughout the day (I seem to remember hearing that you pass through 30-40 cameras on an average day).
If you purchase alcohol on a regular basis using a credit/debit card this would appear in your bank account history, perhaps health insurance companies might be interested in the amount you purchase, this might flag that you have an alcohol problem and therefore affect your insurance premiums. Wouldn't it be interesting for cable companies to provide information on the TV channels/programs you watch to companies online stores so they can target you with appropriate offers.
Technology is making the world smaller, I can make a Voice/Video call from my PC to anywhere in the world using clients such as Skype or IM - but technology could potentially be used to provide a complete history of my life, where I've been, what I've done, what I've purchased, my likes, dislikes, the type of restaurants I visit, even my coffee preferences. So, back to the original question, how private is your private life ?