Copying a successful business plan is safe, and tons of companies are copying Groupon. The differentiating strategies of the more successful copycats are interesting, as is the arms-race and recursion of deal aggregators. I find it fascinating that people sign up for this stuff, because I find it wasteful. This is insane: “In just over two years, Groupon has accumulated 60 million subscribers, more than $1 billion in venture capital and $760 million in annual revenue to become the fastest-growing Web company ever. In December, it declined a $6 billion buyout offer from Google.”