Ron Popeil was a businessman who became an overnight sensation on television with his Veg-O-Matic invention. He and his family invented it and its precursor the Chop-O-Matic in the late 1950s. According to Wikipedia, it sold over two million units. Talk about a direct marketing home run, that was before most people even understood that direct marketing existed!
Interestingly, by featuring these wildly viral videos on television, it exponentially increases their popularity to an audience who may not be familiar with them already. After watching this TV show, it is easy to understand how people can become addicted to those types of sites.
With ads stacked up on top of others, it's not quite as easy as a user giving your message their undivided attention, like they would if looking through your catalog, viewing your commercial, or hearing your radio advertisement. Hence, knowing what your competition is utilizing to communicate their message is a critical factor.