If the future of the internet is social, as some believe, the long-term fate of the world’s largest search engine could rest on how well its social network, Google+ does.

While it has a long way to go before it catches up to Facebook in popularity and adoption, with over 100m users, it would appear that Google is off to a decent start.

But does Google+ have a serious demographics problem?

According to a report published by Website-Monitoring.com, a full two-thirds of Google+’s users are men. What’s more: a sizable number of Google+ users (42%) are single, and the most popular occupation listed is ‘student.’

Add this all up, and if Website-Monitoring.com’s numbers are to be believed, a good chunk of the Google+ social graph is basically young, single and male.

This makes Google+ somewhat unique. According to multiple studies, women are far more prolific users of social networking than men, spending substantially more time on social networks. In fact, as of last year, the only major social network with more males than females was LinkedIn. LinkedIn, of course, is a business-oriented social network, and it’s far less ‘sticky’ than consumer-oriented social networks like Facebook. Obviously, Google is not aiming for Google+ to be the next LinkedIn.

So what does Google+’s lack of popularity with women mean?

For starters, it could make growing Google+ more difficult. Obviously, Google+ is not designed to be a dating website, but we shouldn’t discount the fact that dating dynamics are a part of social networks. Early growth in the world’s most popular social networks (Friendster, MySpace, Facebook, et. al) as they emerged was driven in part by a desire to ‘check out’ and connect with members of the opposite sex.

If Google+ doesn’t diversify its user base (read: acquire more female users), it could become Dudesville, conceivably making it harder for Google to retain and grow engagement with the young male users it already has.

More importantly, a lack of a strong female audience could make it more difficult for Google to turn Google+ into a viable business. Beyond the fact that women tend to be more active on social networks, there’s a strong argument to be made that female users are, in theory, more valuable than their male counterparts. After all, many key segments of the internet economy are driven in large part by women.

The big question: what should Google do?

Trying to control how and where the Google+ userbase grows poses risks for Google, and it probably shouldn’t try too hard to micromanage its social network. At the same time, however, if Website-Monitoring.com’s figures are accurate, product managers and designers at Google should probably start looking at why women aren’t ‘liking’ their social network.