I have advertisement blocked at home, and now at school, I can finally see the banner
Anyway, if I ever have kids, I'll make sure to install dansguardian on my router, block internet after 8 o'clock for their computers, and regularly check their chat logs.
However, many parents don't have the knowledge or the willpower to perform these steps to protect their children from talking to 60 year old men or turning their PC into a zombie.