del.icio.us may be a cool Web 2.0 service but it didn't have a business model that would generate enough money to create a viable business. It turns out the "business model" was getting acquired, and it worked out pretty well after Yahoo! has snapped up yet another start-up. The news was unveiled on del.icio.us' blog. No financial terms were revealed- it all depends on how much Yahoo values users (Om Malik's $38/eyeball formula?) and a well-known brand name. Yahoo's other start-up acquisitions this year include Flickr and Blo.gs. For aspiring Web 2.0 entrepreneurs, VCs and business journalists, the big question is how much Yahoo paid for del.icio.us. Om Malik boldly ventures to make a speculative guess on what's the deal is worth. No one has spilled the beans yet but Union Square Ventures, which led a financing earlier this year, seems happy. Other investors, who took a minority stake last April include Amazon.com, Marc Andreessen, BV Capital, Esther Dyson, Seth Goldstein, Josh Koppelman, Howard Morgan, Tim O'Reilly and Bob Young. Fred Wilson explains Union Square's investment decision here. Amazon, by the way, is also an investor in 43Folders.