Even if users don't mind the ads, it can take a depressing amount of time to integrate ads into a site [1]. Assuming you don't just use adsense, each advertise

Even if users don't mind the ads, it can take a depressing amount of time to integrate ads into a site [1]. Assuming you don't just use adsense, each advertiser often has their own way of doing things and will have one-off requirements for how their ads should behave on your site. That's engineering time that could be used to fuel growth by developing features and working on scaling. [1] I'm speaking from personal experience. For about six months, I worked on nothing but integrating various advertisers' products into justin.tv. Video ad providers are particularly difficult to work with, since it's still quite a young market.