New research from a market research service that tracks Web behavior and social media shows sharp declines among Facebook users in some of the world's biggest markets, including the U.S., Canada and the UK.

The decline in usage for activities such as status updates, sharing content, messaging and installing apps is being called the "Facebook fatigue factor."

"Time has wearied users of Facebook," said Global Web Index researchers. The report also found that worldwide usage of Facebook continues to increase, however, because of growth in the emerging markets.

The report found that messaging friends via the American Facebook platform was down 15 percent last month compared to June, according to an article in MediaPost.com. The proportion of users participating in the "joined a group" activity was down 10 percent in the same period. "The trend is even more pronounced among U.S. college educated 20-somethings, the original users of the platform," the report said.

Emerging markets are driving the growth of social networks, while consumers in more mature markets are focusing increasingly on e-commerce. Some markets, such as Singapore and Turkey, use the Web significantly for both, but tend to skew slightly one way or the other, MediaPost said.