It's been a while since I put a blogsticker in here.
You know you've done a successful advertising campaign when it slips into common usage and starts appearing everywhere. The original ad was "Got Milk?" Now we have this:
ThinkGeek sells a t-shirt saying "Got Root?" and a friend has a bumper sticker saying "Got Jesus?" which is a lot less scary than the big red truck driving around with black windows and a "Vegetarians Taste Better" sticker.
But nothing beats the "Behold, the Power of Cheese" ads.