Moo.com shows this very interesting popup on their homepage (notice the red box in the screenshot below)–
This is a very clever strategy. Moo is making it sound like this invitation (free shipping on next order) is for people who saw Moo ad. What do you think this does? It makes visitors who didn’t see the TV ad want to signup because they don’t want to be excluded from this exclusive group of TV ad viewers. Had the popup text just said, “Sign up to our MOOsLETTER and you’ll get FREE SHIPPING on your next order. Yay!” it would have been less enticing, and less effective.