IMO, each generation faces different landscape of software and hardware infrastructure and end-device. The existing social net work and communication solutions can't meet the delta of this generation's needs against previous ones, hence there comes the big unmet needs from the emerging generation. However, solution builders have to be close to this generation enough to have enough sense/instinct of the delta to build products that can actually cover those delta.

Just my observation and not being described accurately and clearly enough here. But I hope you get what I'm trying to say.

Search went through many shifts, but hasn't since Google. When a new technology matures, someone eventually figures out how to dominate it, and does.

The difference with computing was on-going Moore's law (forever young), which now slows/ends. Worse, though they still shrink, the cheapest node remains at 28nm. Cheapness fuels revolution. Peak silicon has passed.

We could get a new technology (like fracking etc and peak oil), as Kurzweil suggests for the singularity.

>When a new technology matures

I don't believe search is mature. We haven't seen a lot of innovations in web search for a while and what we know as web search is probably the best Google can do. It's probably not the best possible web search though. Just the best from Google.

The reason nobody is there to challenge Google is because noone has come up with a way to fund a web search engine other than through ads. Challenging Google probably also means challenging the whole ad industry. It's a rough climb.