It's a good question. I'd flip it around a bit and say that if you're a search engine that: - Hosts commercial advertising content (not the entire web; only p

It's a good question. I'd flip it around a bit and say that if you're a search engine that: - Hosts commercial advertising content (not the entire web; only product and service offerings) - Charges for hosting - Has a highly qualified audience that genuinely wants to receive relevant advertising (based on requests being user-initiated, not software-initiated) - Claims credit for revenue generated as a result of providing relevant advertising ... then you're likely to be able to cover the costs of developing and maintaining the system.