"They're calling it the Mark Zuckerberg bump," says Jessica Guynn at the Los Angeles Times. On Wednesday, a day after Zuckerberg made his first public comments since the company launched its disastrous IPO in May, Facebook's share price climbed more than 7 percent to close at $20.93. While the stock is still 45 percent below the IPO price of $38, it was a rare good day for Facebook, which has been plagued by concerns that it doesn't have a model for sustainable revenue growth. Investors described Zuckerberg, who delivered his remarks before an audience at the Tech Crunch Disrupt convention in San Francisco, as "calm, cool, and collected," which gave the beleaguered company a badly need jolt of confidence. Are Zuckerberg and Facebook back?

Yes. He hit all the right notes: Zuckerberg "decisively mastered his first Q-and-A session" since the IPO, says Carl Franzen at Talking Points Memo. He is keenly aware of Facebook's need to transition to smartphones, admitting that the company's "biggest strategic mistake" was wasting two years trying to code its app with a homegrown programming language. He also piqued the curiosity of investors with his references to Facebook's search tool, which attracts a billion queries a day even though, in Zuckerberg's words, the company is "basically not even trying." And by addressing the company's concerns "confidently" and "candidly," Zuckerberg showed he knows how to usher in future monetary success. 
"Facebook CEO Mark Zuckerberg aces first post-IPO interview"

No. Actions still speak louder than words: Sure, "Zuckerberg gave the impression of a leader who knew what had gone wrong and was confident about his next moves," says Erik Sherman at CBS News. But "confident talk from chief executives is about as plentiful as CEOs themselves." Facebook's smartphone conundrum remains the same: "Ads are tough" to fit on a mobile screen, and "if people dislike the ads enough, [including them] could be counterproductive." Facebook's stock price will "likely shoot down again the minute it becomes clear that wishful thinking isn't rapidly turning into fact."
"Facebook shares pop, but can Zuckerberg follow through?"

But for investors, words do speak loudly: "The market's strong response to Zuckerberg's talk shows that he can" at least "affect perceptions of the future outlook," says Matthew Yglesias at Slate. Of course, "delivering future profits and delivering optimism about future profits" is different. But perception matters. Just look at investor-favorite Amazon, whose value on the stock market is a "crazy-high 314" times its actual profits. Any "shift in sentiment is enormously important" — if not for a business' future profits, than at least for its current stock price.
"Facebook's secret strength"