I was asked this once and it’s simply a matter of resisting the temptation to sell out.
This blog gets a bit of traffic, it *could* generate probably $5 a month through adsense… so why don’t i put ads on it?
I don’t want to cheapen the site and drive users away… a blog is a personal website… not a commercial one. Using adsense on such a site would be selling out and would mean i’d be putting profit over quality. Adsense ads are pretty big, pretty in your face and therefore take up a good chunk of any site.
I will never put banner ads or skyscraper ads on this blog no matter what the price as this is MY space, people come to it to see MY work/entries… they don’t want to see ads.
Sure, if i was getting 1000 uniques a day, had a PR5 and stable alexa rank, i would sell text link ads or something very blended and unobtrusive simply because it’s easy money and would keep me motivated. So if anyone comes looking for a banner ad, you know where to go 
However if you want to buy a few text links for big bucks, drop me a line 
