According to eMarketer, a digital marketing analysis firm, Facebook is still the number one social network by a large margin, but second and third place go to Google's Google+ and YouTube.

That Facebook is number one, with its 1.11 billion members , is no surprise. EMarketer believes that just over half, 51 percent, of all internet users visit Facebook at least once a month. The company also stated that worldwide Facebook penetration will only continue to grow higher, reaching 60 percent of internet users by year's end.

Behind Facebook, things get more interesting. There are numerous companies fighting it out for second place, with Google+ out front at 26 percent of internet users. Google+!? Yes, Google+. As eMarketer stated, "In the US, Google+ gets limited attention, though its user base is growing. Worldwide, Google+ has been much more successful."

This analysis agrees with GlobalWebIndex's numbers. GlobalWebIndex found in January 2013 that Google+ had moved into second place , with approximately 343 million active users.

YouTube, which both analysis groups now consider a social network, is right behind Google+ with 25 percent. Combined, eMarketer concluded "that Google, which owns YouTube, is giving Facebook a run for its money in the global social network space".

Of the other major Western social networks, only Twitter, with 22 percent in fourth place, was above 20 percent. Twitter, by eMarketer's count, is growing quickly. "Between Q2 2012 and Q1 2013, active users of Twitter rose 42 percent globally."

The other most popular global social networks, those with more than 10 percent of the global social network market, are all regional Chinese networks. The top three, in order of popularity, after Twitter are Sina Weibo, at 21 percent; Qzone, at 21 percent; and Tencent, at 20 percent.

Of the other Western social networks, only LinkedIn, at 8 percent, and Pinterest, at 4 percent, broke into the top 15 global social network list. A better way of describing these networks isn't with the word "Western", but non-Chinese.

As eMarketer described the global social network market, "Chinese social networks garnered among the greatest percentage of users worldwide, a reflection of both the vastness of the social audience in China and the limited availability of foreign properties, like Facebook, in the country." At the same time, if you look at the countries with the greatest rate of growth in social networking, you'll find, in this order, Indonesia, Saudi Arabia, Singapore, the US, and Russia. Much of this new growth is being driven by smartphone and tablet users.

What all this means for business is if you're going to spend marketing dollars on social networks, the biggest bang for your buck in most countries will be from either Facebook or the Google+/YouTube pairing. Twitter would be your next choice. As for the other social networks, unless you're looking to the Chinese markets or want to reach business people on LinkedIn, they're far in the back.

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