Google+ is the third wheel of social media. Not as popular as Facebook and lacking the niche-focus of LinkedIn, it straddles the line between personal and professional networking tools (we won’t count Twitter since it’s more of a micro-blogging platform).

Google has made forays into the social space before, but while Google Buzz fizzled out after only 11 months, Google+ has made better headway, gaining 100 million users in under a year. By comparison, 2-year-old Pinterest has only 10.4 million users.

Despite this disparity, Pinterest has been hailed a remarkable success. It won the Breakout Digital Trend award at SXSW 2012, is fawned over by designers, and earns monikers like “digital crack for women” (males make up nearly 70 percent of the Google+ user-base, so perhaps it’s the Pinterest for men?).

Meanwhile, Google+, which grew its user base faster than any other social network – ever – remains haunted by skeptics.

Not Facebook, not LinkedIn… What is it?

Some might say that Google+ is to Facebook what Pepsi is to Coca-Cola: same taste, different logo, less popular. So how does it distinguish itself?

For starters, Google+’s stream is roomier. Since it doesn’t have sidebar ads (yet), there’s much less clutter. Photos are larger and posts and updates are often text heavy.

Another design novelty is the Circles function. Rather than having all of your contacts funneled into the same category, G+ allows users to control who sees what by grouping contacts into different circles. So you can have a “friends” circle, a “colleagues” circle, a “family” circle, and so on.

Yes, Facebook provides a similar option (which it introduced in response to G+), but the follow-through is tedious: Users have to go behind the scenes to adjust settings. By comparison, Google+’s circles feature is seamlessly integrated into the user experience, making it easy and intuitive to organize contacts, and control who sees what.

The network also effectively facilitates content-sharing, since people can follow others without their consent, just like Twitter. But unlike Twitter, followers who you don’t follow back won’t see any of your posts unless they’re categorized as “Public.” Confusing? Yes. More organized and privacy-friendly? Definitely.

Perhaps the biggest departure from Facebook and LinkedIn is Google’s live video feature, Hangouts, which allows up to 10 computers to communicate simultaneously. So far, reviews of hangouts have been positive thanks to its ease of use, quality of streaming and extra features. For instance, users can share their desktop screens as well as Google Docs, making it a great choice for video conferencing.

Brands on Google+

So if Google+ is only slightly different from Facebook, how (or why) should brands use it?

A number of high profile brands are doing well, relatively speaking, on Google+. Clothing brand H&M has over 400,000 followers. Samsung and Pepsi have over 300,000 followers, along with Burberry, Starbucks and Coca-Cola. Even Facebook has its own G+ page (with over 40,000 followers).

Those numbers may pale in comparison to the same brands’ Facebook pages (H&M has over 10 million likes) but one problem with Facebook and Twitter is that brands often treat them like broadcast channels. The platforms just weren’t built for in-depth conversations.

Google+ hangouts, on the other hand, are as close to a one-on-one personal conversation as a social network can get. The Muppets brand used hangouts to great effect before this year’s blockbuster. Dell has hosted hangouts to discuss technical issues, relay news, and discuss new products. Even President Obama has jumped on board.

The downside is that only a limited number of people can join the conversation, so it’s best for brands to target influencers and then find other ways to transmit the content, such as streaming it on YouTube afterwards.

The bottom line: Instead of attempting to build a Facebook doppelgänger community on Google+, brands may be far better off directing people to hangouts or using G+ to begin conversations and showcase content – in effect, like a more social version of Tumblr.

As Cadbury can attest, it’s also a novel place for a product launch. The confectionery company used the platform to launch its Dairy Milk Bubbly chocolate bar with the sweetly social tagline, “The Cadbury bar that’s great for sharing.”

H&M has one of the more successful Google+ pages.

The ghost town problem

Perhaps the biggest blow to Google+ came in February 2012, when comScore reported that people spend an average of 3 minutes a month on the network. That’s a pittance compared to Facebook’s 7 hours.

Another report published in May by RJ Metrics indicates that interest is still waning, with average posts receiving “less than one +1, less than one reply, and less than one re-share,” reports Austin Carr of Fast Company.

But averages don’t tell the whole story. The reality is that Google+ has a much smaller base of active users (those using G+ specifically, rather than G+ “enhanced” services like YouTube) who log in for more than 3 minutes a month, which puts a spin on the stats.

With the addition of Google+ Pages, there has also been a reported uptick in the number of unique visitors to the network each month. But since Google won’t release monthly user reports, most of these stats are speculative.

The trick, then, is for brands to figure out what demographic is using Google+ and whether they’re ripe for engagement. Right now, Google+ is a relatively small pond, making it much easier for brands to become big fish.

So is it worth it?

It’s impossible to discuss Google+ and ignore that for most people, Google’s search engine is their primary point of entry to the web. As Google’s VP for engineering Vic Gundotra has put it, G+ is meant to be a “social layer” on users’ web activities.

If Google has its way, the web will eventually be indistinguishable from a social network, with every page connected in some way back to Google and to its advertising network (which is perhaps why there’s such a disparity between what critics call a lack of stickiness and what Google calls Google 2.0).

So marketers may want to hedge their bets and engage. As the New York Times’ Nick Bilton recently wagered, “Google+ is here to stay, no matter what.”

Editor’s Note: Check out Sparksheet’s first Google+ Hangout with Joe Pulizzi and Arjun Basu.