This is a $5 Radio Shack notch filter in a fancy box being sold for $90. It blocks the signal that the cable box sends back to the cable co. whenever you access premium channels. When you block the signal the box just stores the information until it can send it successfully. Also, these boxes are usually polled as well. If the cable co doesn't hear from the box over a month it may call you up and ask to service or replace the box. So now you figure you should take your block off before they show up, and when you do the box sends the whole last month's worth of pay channel viewing to the cable co. Whoops!
Stealing cable service is a federal crime (
http://www4.law.cornell.edu/uscode/47/553.html) and usually also a state crime. The govts like to prosecute it because they are getting a cut from cable franchise fees. When you don't pay for cable you are not paying the govt and they don't like that.