When you’re the hot new web product on the block, you quickly find that imitation is the most irritating form of flattery. But startup Groupon has turned some lemons (namely, international clones in Russia and Japan) into the sweet lemonade of international expansion. Over the past few months, Groupon’s core feature set has been cloned and ripped off to no end by a significant number of companies in Silicon Valley; these startups are horning in on Groupon’s share of the U.S. market and, more importantly, U.S. advertising dollars. Read more...