NEW YORK (AdAge.com) -- UrbanDaddy is an e-mail newsletter that's surprising for a number of reasons, not the least of which is that it's only available by invitation. And yet it has signed up 300,000 young lawyers, bankers and brokers and now puts out editions in five cities. Its successful strategy is also noteworthy because of its Web 1.0 simplicity and a dogged determination to build a brand that speaks with a singular voice of journalistic authority. No blogs or UGC here. It's also signed on a blue-chip list of advertisers including Sony, Samsung, American Express, Belvedere Vodka, Ralph Lauren and Hugo Boss.