Here's a sin of which many online marketers are currently guilty. The advanced targetability of online advertising is simultaneously a huge benefit and a major drag.

The benefit, of course, is that advertisers can use targeting to concentrate their media efforts on the sweet spot of their target audience.

The drag is that a lot of advertisers confuse "sweet spot" with "entire market," and they overtarget their ads, often with detrimental results.

A quick war story: in 1998, I worked on a telecom account where the client was advertising ISDN and DSL within a certain geographic footprint. We employed geotargeting in order to minimize waste and to cut back on the number of folks ringing up the call center from outside the service area. Along came a proposal from a well-known search engine to serve the client's advertising only to people looking for ISDN or DSL within the target geographies. Geotargeted keywords sound like a good idea, right?

Wrong. As it turned out, the search engine had location data on only a small fraction of its user base. Overlaying the audience of folks searching relevant keywords with the tiny pool of folks on which they had geographic data resulted in a microscopic potential audience, indeed. After slamming the same 11 people over the head a few hundred times with our ad, we canceled the order.

In retrospect, we shouldn't have overlaid the two targeting filters. ISDN and DSL had such low penetration compared to dial-up back then that we could have easily forgotten about the keyword filter entirely and had a successful campaign.

These days, advertisers make the same mistake very frequently. If the demographic sweet spot for red rubber balls is Men 18 to 24, online campaigns are often focused on that demo with laser-like precision. And that's a shame, because there's really nothing preventing a 35-year-old woman from buying a red rubber ball.

Don't assume a target audience is a market, or vice versa. One of the differences between television and interactive is TV's spill into demographic audiences other than the one targeted. While certain television campaigns might be guaranteed against Men 18 to 24, they also deliver some Women 25 to 49 in addition to the buying target. Some of those women buy the product. Why should it be different for online ads?

Experiment with loosening your targeting restrictions a bit. You might be pleasantly surprised by the result. Obviously, your mileage may vary.