It really does work...I hacked all of our computers about a year ago that way. It'll slow down a couple of web sites, but most it'll speed up. The best part is it's not just effective against pop-ups, but also banner ads and spyware (that can't call home anymore).
Only annoyance is there will be some "legitimate" web sites you won't be able to get to because they go through some hit-tracker type of website before the main site. But I figure that's their loss, not mine...
Yes, some sites rely on income from adverts. But that should not be our problem...
It's not their loss if they rely on ad revenue to support publishing the site. The fact that you won't be showing up will save them money. If you have their ads blocked, you are of no use to them.