Currently Facebook is undeniably the leader in traffic generation, but this may not last forever. On older sites with well established Facebook and Twitter following, Google+ has little chance of taking over simply because the blue social networks have been around longer. However, on new sites Google+ does have a chance. On two fairly new sites I'm running, I was surprised to learn that Google+ referral traffic took over Twitter (Thorium Forum and 3D prints of the World) and on one of them G+ is already on the heels of Facebook. I don't have a comprehensive study on Google+'s effectiveness for new sites compared to the other two giants, but I heard similar good experiences with Google+ from other webmasters.
The reason why Google+ is catching up with Twitter can be easily explained. According to stats from September Google+ has approximately the same 500M+ active users as Twitter.
But Facebook is still at least over 2-3 times bigger than Google+ by any measure. On big sites Facebook generates over 20-50x more traffic than Google+. So how come Google+ can still be competitive with Facebook on new sites? I think I know the answer. Let me explain a simple strategy you can follow to make the most of Google+.
There is an effective and honest way to grow your Google+ readership and referral traffic: join and use Google+ Communities.
Communities on Google+ are designed to work a bit like old-school forums where people with specific interests come together to discuss world news and their personal experiences.
Do not simply post your content on your feed for people who circled you. Search for Communities that match the topic of your posts and post into them. The posts will be visible to people who circled you and to the members of the community. Some of these Communities have tens or even hundreds of thousands of members. When you post in these Communities you directly reach people who signed up for the kind of content you're offering. Your posts will bring real value to the followers of these communities. It is also a great way to generate traffic to your website and gain new followers. For new sites this can be invaluable.
You can't achieve the same effectiveness on Facebook or Twitter because they are primarily designed for communication with your friends, not interest groups. There are groups on Facebook but they are somewhat hard to find and generally smaller than on Google+. You can also use hashtags and they work on Twitter, but virtually nobody browses content through tags on Facebook.
You can buy yourself followers on both Facebook and Twitter for a new website, which is not possible on Google+ at the moment. Maybe this is the reason why Facebook and Twitter is not interested to create communities similar to what Google+ has. They want you to buy the first few hundred followers instead of growing them organically through communities. Google on the other hand is not interested in making money this way. Google makes money on gathering information on users so they can target ads better.
Does it make sense to invest time in growing your Google+ followers? The answer is clearly yes. Besides the already mentioned traffic generation there are two more reasons why using Google+ is a good way to spend your valuable time.
Search traffic is usually the biggest single source of traffic on sites. Google+ activity around your website without a doubt helps with Google Search rankings.
Finally, the G+ network is growing more aggressively in both number of users and features than any other social network Today. You can see Google+ being the most capable in this comparison of supported features post, which will eventually lead to bigger number of users too. It is likely that Google+ will be the second biggest social network within two years for most sites and will challenge Facebook within five.