Answer: Facebook had the most active usage in the fourth quarter of 2012, followed by Google+, YouTube and Twitter, according to a report from the GlobalWebIndex.
The index defines active usage by whether someone used or contributed to the network in the past month. Twitter saw the most growth with a 40 percent increase across the global Internet population compared to the previous quarter.
Here's the breakdown of active usage on each network by worldwide Internet users:
LinkedIn came in 10th after a number of Chinese-only networks, Myspace came in 14th after another set of Chinese-only networks, Pinterest came in 16th, and Tumblr came in 19th.
Anecdotally, plenty of educators are using these tools to learn from each other, share resources with students and strengthen ties with the community. Here are just a few examples of how educators are taking advantage of social networks: