There have been studies on how trends spread, how there are a number of key individuals in social groups that decide what's cool and what's not, and that some trend explosions can be traced to a few individuals.

For instance, the movie Office Space didn't do very well in the theaters, but it's acquired a cult following ever since. One of the plots revolves around a red Springline stapler, and provides some of the most quotable moments. One problem - Springline didn't sell red staplers - the prop department took a stapler and painted it red. Springline didn't pay much attention, until it started getting requests from nowhere for their red stapler. They finally produced some and put it on their website. It became a Slashdot story, and the website was overrun.

One way to make money from weblogs (indirectly) is to monitor them for similar trends, and sell this marketing information to companies. Springline had no idea about the demand for a non-existant product, but a freelance marketer could have noticed the blog trend, projected sales, and sold this info to Springline. One problem - it isn't a very repeatable service. I doubt Springline will ever have a hot product like that again...

However, trust networks may reveal the trendmakers in the blog community. If a trendmaker is given a product, he or she may write about it, and you have free word-of-mouth advertising from a source that many already trust. Think of how bad TiVo's media advertising is, but how effective the word-of-mouth advertising has been. At worst, popular bloggers get free stuff...

Of course, both of these are just gay "advertising... but on the web!" ideas. But sometimes, you just have to go for the gay.