Blogger Jason Kottke is going pro. He has quit his job as a web designer and is asking his visitors to donate $2.50 per month to help him pay his rent, buy a new car and take that vacation to Hawaii.

Kottke's approach reminds of Salon.com's efforts to become a subscription based online publication (the company breaks even, but that's it). Or attempt back in 2000 to get web visitors to pay $1 for each chapter of a book he posted on the web. The project got off to decent start, but faded further down the road.

Since Kottke is the first who is trying to do this, he might very well succeed. But blogs through a subscription model lack an essential economic feat: scarcity. With an endless supply of blogs, there is only an emotional incentive to pay the blogger for his work. If he stops blogging, we'll just visit some other site.

That's why advertising and the web are made for each other. Advertisers look for exposure though an abundance of eyeballs, not scarcity.