Google’s AdSense program is fantastic, a category killer. A good way to make money, a tasteful way to do ads, and a dramatic new way to turn hobbyist or personal websites into a more-than-break-even source of revenue.

Nick Denton, no stranger to the attempt to make a profitable blog, has even predicted AdSense will have an impact on site design, though of course he was characteristically cynical about his own prediction just two days later. Still, I agree with Jason Shellen’s assertion: smart use of AdSense placement will probably outperform most current banner-based systems.

But there’s a few critical problems. First, only some categories of content will truly benefit from these ads. Matt Haughey’s PVRblog has been quite succesful, in terms of PageRank, traffic, and ad dollars. But part of the reason for that last success is that the cost per click on Tivo-related keywords is extraordinarily high. Some quick-and-dirty cost calculations on the phrase "Tivo upgrade" as an AdWords ad shows the cost per click to be about $4.50. The word "Tivo" alone is worth almost $3 a click, and generates 250 click-throughs per day. With PVRblog showing up near the top of a lot of Tivo accessory-related searches, the site is bound to get a nice piece of those click-through pennies.

Most topics aren’t so lucrative, though. You could work backwards, querying for the most valuable search terms and building sites around them. Web hosting is a perennial text ad favorite, with the word "hosting" bidding at up to $15 a click and Google’s tools predicting 2400 clicks per day. That’s more than $35,000 in ad revenue generated by one keyword every day. Great sites, and great weblogs in particular, aren’t typically created by designing around a particular keyword, of course. So you have to write what you know, what you’re passionate about. And if you happen to like Jai Alai instead of hosting, you’re only getting a dime per click.

There’s a far more serious problem with AdSense, though. The approval system is capricious, even arbitrary. It’s understandable that Google wants to make sure sites aren’t just ad farms, and it’s in everyone’s interest that quality be maintained, ideally by human verifiers. Nobody wants to see those sad Red Cross PSAs that take the place of house ads on poorly-indexed sites.

The human verification process at Google, though, is uncharacteristically opaque. I’d assume they factor in the ads which would run on a site before approving or denying an application, and if I take a look at my site’s potential ads, I see some of value. Ads specifically targeted to weblog software, Manhattan computer repair, New York hotels. These all seem relevant and valuable to me, but I’ve been repeatedly rejected.

It’s not just sour grapes on my part. Take NYC Eats, a great little niche weblog. Aaron‘s brilliant little AdSense senser shows some potentially lucrative ads, which makes sense since the letters "NYC" by themselves cost two dollars a click. But no AdSense approval there. The problem is the wording in the program policies:

In general, we do not accept personal pages, chat sites, or blogs into the AdSense program. However, if a site contains targeted, text-based content and/or provides a product or service, we may consider it for participation.

But Puzzleblog (formerly Scrabblog) is a personal site and a blog, and there’s no policy anywhere which describes why one site is accepted and another denied. Daring Fireball is an excellent site, but why does it have AdSense ads when Jeremy Zawodny‘s site doesn’t?

Some of these concerns have been covered before, of course. But we all love Google for being transparent and comprehensible. I take it on faith that PageRank is consistent, even if its actual rationale is secret. For example, it frustrates me that googling TypePad doesn’t have the TypePad.com site as its first result, but I’m assuming that having somewhere close to 100,000 pages linking to TypePad.com with the exact same text looks like a Google bomb and so it gets filtered out. Fair enough.

The fact that a human rejected my AdSense request with an ostensible rationale troubles me, even if I understand it. Though I’m clearly not as good a writer, I don’t see an appreciable difference between my site and Steven Johnson’s in terms of being blogs or personal sites. And that seems out of character for Google. The vaunted Google index has, thus far, been a meritocracy. The economic ecosystem that could emerge through AdSense deserves the same equality of opportunity.