I sent an e-mail message to a friend telling him about Adblock Plus, an easy-to-use free addition to the Firefox Internet browser that deletes advertisements from Web sites. That subject line of his reply summed it up quite nicely. What happens when the advertisements are wiped clean from a Web site? The larger importance of Adblock is its potential for extreme menace to the online-advertising business model. After an installation that takes but a minute or two, Adblock usually makes all commercial communication disappear. No flashing whack-a-mole banners. No Google ads based on the search terms you have entered.