A simple google for 'ad-block' will reveal a number of browser plugins that will do the trick for you. I'm sure you can appreciate why we find it pretty irritating though!
We do work relatively hard to find a balance between making ads generate site income yet not ruining the usability/experience of the site. One of the things we shouldn't be having are pop ups/pop unders though so we'd ask for help in identifying and removing them if they do appear. A screenshot/URL and description of when it happens would be very useful for this.
Are we supposed to be getting very loud unwanted video ads? Perusal of the Ginger thread was rudely interrupted by loud music, which I had no idea how to stop and no idea where it was coming from. Also generated unwelcome attention from my 8 year old!
Do you really want to know? It's a long boring techy tale. However, the short version is because they (Google) are clever chaps and figuring out relationships between apparently innocent data is what they do for a (very good) living.