GOOG will be the biggest company in the world someday. Self driving cars will get them there.

If AAPL bought a company like YELP, that's when I would say they're fucked and get out. That would be a true sign that they don't know what they're doing and just trying to do ANYTHING to get some mojo back. YELP and AAPL have very different business models and they don't align at all IMO. Web advertising is rapidly dying - that's why GOOG is getting into other areas of exploration rapidly.

I see TWTR providing far more business and economic value than YELP. Certainly long term. TWTR is, what, 3x the size in market cap? I see them as 100x more valuable of a company personally. It's all funny money and smoke and mirrors, though. Remember when GRPN and Living Social were the darlings despite not making any real money? Fundamentals matter when investing for the long term, but short term technical measures almost always win.