Online trading platform Intrade has ceased all trading activity pending an investigation.

BBC: Intrade shuts amid investigation

Other Windy City players that have made headlines in recent months include (though not in as infamous a fashion as Groupon) mobile marketing firm Vibe Media, food delivery and restaurant finder company GrubHub, online trading platform optionMONSTER (home of tradeMONSTER) and personnel management software company SilkRoad.

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CafePress, an online retail platform, is trading at just 13 times future earnings.

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