I think the ad-based business model for internet companies could possibly be toppled in the next few years: 1. The ads are becoming increasingly ineffective, the CTR keeps falling, even as the ads are being personally customized. People are growing biological ad-blockers that block ads subconsciously. There is an interesting theory of "Peak Advertisement": http://peakads.org/. 2. The value of digital assets/services are being recognized, and people are more willing to pay for online services.

So maybe in the future internet companies will rely more on customer's subscription fee + ads that are more transparent (sponsored content).