Facebook's greatest asset is its user base, which has historically grown at a breakneck pace and which has been assumed to be composed of rabid Facebook fans who love the platform. A large, growing and enthusiastic user community is the entire basis for any optimism about Facebook's ability to make money.

But last month, the American Customer Satisfaction Index (ACSI) released a report showing that Facebook , the lowest-ranking social network for customer satisfaction by far. Worse, new rival Google+ scored highest with 78.

Meanwhile, Capstone analyst Rory Maher reported last month that Facebook is , dropping by 1.7% in the US over the last six months.

This week, the company reported to the U.S. Securities and Exchange Commission that about 83 million Facebook user accounts are duplicate, misclassified or " ."

From a business perspective, perhaps the most devastating developments this summer are widespread questions about the effectiveness and even the legitimacy of Facebook advertising.