Google’s upbeat comments about YouTube, and the general state of its business in Q2, are paying off in a big way today: The company’s stock price is up nearly 16% in mid-day trading, and touched a new all time high $703.00.

How much is that worth? Consider this: Investors value Google at about $369.6 billion, which is $51.1 billion more than it was worth yesterday. Today’s increase, in theory, would be more than enough to buy all of DirecTV ($47.0 billion), Netflix ($42.1 billion), or Yahoo ($36.4 billion).

Indeed, today’s change at Google is bigger than the entire value of every major media company except for Disney (with a $200.6 billion market cap), Comcast ($160.5 billion), Time Warner ($73.2 billion), and Fox ($68.5 billion).

Wall Street’s responding to several encouraging disclosures last night when Google beat analysts’ Q2 forecasts with adjusted net earnings of $4.83 billion, up 17.7% vs the period last year, on revenues of $17.73 billion, up 11.1%.

YouTube helped to drive the results, a surprise to those who feared it would suffer as competitors including Facebook increase their video offerings. Spending among the top 100 advertisers was up 60%. And watch time improved 60% from last year, the fastest growth rate in two years.

Pivotal Research Group’s Brian Wieser’s back-of-the-envelope calculations suggest that YouTube accounts for 14 billion hours of viewing each month.

It “could become much more of a TV-equivalent if it begins to invest more meaningfully in what most advertisers would consider to be truly ‘premium’ content, where advertisers can better build their brands,” he says. “Advertisers absolutely want more digital video advertising rather than conventional banner ads, for example, and YouTube has more of it than any other digital property, although Facebook will have the capacity to match them.”

Growth at YouTube and mobile search ads “more than offsets” deceleration in the older search businesses, Nomura Securities’ Anthony DiClemente says.

And Morgan Stanley’s Brian Nowak connects the dots with the slow down in TV upfront sales, and broad ratings declines. The weakness in traditional TV at a time of accelerating growth at YouTube “is probably not a coincidence.”