If you've never experienced an over-optimization penalty, some people think that you haven't been trying hard enough. There's a big difference between spamming the search engines and pushing the line to find out where it breaks. (Skip to "Does an Over-Optimization Penalty Exist?" by Bill Hartzer)

It's easy enough for many search marketers to say that they've never had a penalty and they've never had a site banned. But that brings about a question of how many new techniques they are experimenting with. While I'd never encourage someone to take chances with client sites, most of the really effective SEM firms out there have their own internal sites that they use for testing purposes. Chances are good that most of them have crossed the line at least once with these test sites.

Regular Search Engine Guide contributor Bill Hartzer examines the concept of an over-optimization penalty today in his featured article: "Does an Over-Optimization Penalty Exist?."