Silicon Valley's favorite guessing game — when will Facebook founder Mark Zuckerberg take his company public on Wall Street? — was whipped up into a frenzy by a fresh Wall Street Journal report that targets a mid-2012 initial public offering. "Facebook Inc. is inching closer to an initial public offering that it hopes will value the company at more than $100 billion, according to people familiar with the matter," writes Shayndi Raice, who adds that the valuation would be "greater than twice that of such stalwarts as Hewlett-Packard Co. and 3M Co."  The Journal says the deal is supposed to go down between April and June of next year, but it certainly won't get any help from Facebook higher-ups in pinning that estimation down. As they have since the initial whisperings of a rumored IPO started last year, Facebook executives are playing hard to get. "We're not going to participate in speculation about an IPO,"  Facebook spokesman Larry Yu told The Journal, a line which follows the lead of savior-genius Zuckerberg's quote to the Los Angeles Times that he doesn't spend "a lot of time on a day-to-day basis thinking about" an IPO, and board member Peter Thiel's "maybe we will, maybe we won't, maybe it's definitely happening in 2012" flirtation with the media.  Sure Mr. Yu and his colleagues "aren't going to participate in speculation," but they surely have no problems stoking it.