Facebook Earnings: Profit Rises Amid Growth in Mobile - WSJ.com

So maybe not "Facebook fatigue"

"Facebook also tried to allay concerns about user growth Wednesday. In the wake of some recent reports citing user fatigue with the social network, Facebook said the number of its daily active users jumped 26% year-over-year to 665 million people while monthly active users climbed 23% over the same period to 1.1 billion.
Facebook continues to see "high levels of engagement globally across our whole community," said Mr. Zuckerberg."

Facebook Earnings: Profit Rises Amid Growth in Mobile - WSJ.com