Here's Mark Zuckerberg speaking at Stanford back in November 2005. The Facebook founder says,

What's the thing that I measure the most? It's that 70 percent of the people come back to the site everyday and making sure that remains. Not just because we're doing some gimmicky thing.

More than two years later, Facebook continues to resist the temptation to engage users through gimmicky features. Take a look at the below list of Facebook's applications with the most activity, and see for yourself.

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