You bring up a good point: Do ads work to get user adoption? I'm not sure - I certainly haven't heard of an app that used ads for more than just jumpstarting the viral loop.
Are there examples of apps that have gotten adoption through ads?
Hotel Tonight and Uber both advertise a LOT-- I assume they have the LTV to support the cost of buying a user via ads. I've spoken to a lot of mobile ad experts and, because the targeting power isn't yet there, they say it's cheaper to buy a user with plain ol' web ads than mobile ads (unless your a game).
Are there examples of apps that have gotten adoption through ads?