I think the return on investment probably needs to (and intends to) include the public relations events (like the Wired article) created, as well as direct conv

I think the return on investment probably needs to (and intends to) include the public relations events (like the Wired article) created, as well as direct conversion rates. It's entirely possible DDG / Gabriel will have more new users from that article than from a month of the billboard, but of course the article wouldn't have been written if he hadn't done something novel like old-school advertising a new-school product.