Tim O'Reilly responds to accusations that O'Reilly sites are funded by search engine spammers, and reviews some of the challenges currently facing ad-supported Web sites:

I do recognize that Google's preferred form of advertising -- context-relevant ads via Adwords -- is a real advance in making ads useful and targeted. However, at least so far, our experience has been that Adwords revenue will not even remotely make up for the other forms of advertising we carry on our sites. So our alternatives are to: a) convert the sites from advertising to subscription, b) continue to support them via advertising, or c) shut them down.

Simply put, we pay O'Reilly Network contributors for content, and we pay our staff to develop and maintain the sites. The money to pay those people comes from advertisers. Readers get the content for free, and advertisers pay for the chance to get those readers' attention. It's expensive to create a quality website with original technology content--many O'Reilly Network competitors have gone by the wayside in the past few years. I can assure you that we're not merely "a publishing empire trying to bring in a few more bucks," as one person commenting on Phil's blog claimed. Offering ad-supported content is not a hugely profitable business, and we're just as much "someone literally trying to pay a bill" as the small guys who Phil's commenter gave a free pass to on this issue.