For what it's worth, Facebook does the same thing with big corporations that pay it millions of dollars for year-long advertising deals (from which GM famously pulled out in recent months). As far as I can tell, paying them a giant chunk of cash gets you a dedicated sales team that occasionally visits your office, helps you acquire "Likes" for your page, and tries its best to explain how to maximize uptake of your posts via the context algorithm.

Seems a heck of a lot cheaper just to churn out relevant and high-quality content instead, but what do I know? I realize I'm being fairly glib here, but your hypothetical analogy about Google is pretty spot-on. Google didn't need to hire a swarm of sales reps to explain SEO to advertisers; instead, it made search advertising fairly turnkey. It realized, rather astutely, that it was better served owning the market for search advertising than wasting its efforts hand-holding big clients on SEO. (Furthermore, it realized that getting into the SEO business would necessarily conflict with its stated desire to deliver the best results to users). And so it ceded one monetizable space for another. Facebook might want to consider this choice.