In my previous job we had massive resources for finding information often these involved form filling just to get permission. The internet however more often than not reveals all the information required especially if you know the web sites to look on (some government, some not) even the color of someones front door or place of work can easily be researched using Google maps/street view once other information is found. It just takes time.
If you have owned a business, are on the electoral register, have featured in a local newspaper, have an advert advertising something on flee bay or are simply on the internet all the pieces can be put together eventually. Unnerving perhaps but it is the way the world is now. Look at Samsung's latest smart TV's, they have just reported that the cameras on them can be used to look into your home due to a fault.
Obviously they are fixing it.
