Pew has released findings from a recent telephone survey (n=3,001) that asserts 4% of PC Internet users and 7% of mobile Internet users are on location-based services such as Foursquare or Gowalla. The first number is in general agreement with Forrester's survey numbers. There are other surveys that have found somewhat higher LBS usage numbers.
Pew found LBS users tend to be male and under 30:
One of the "issues" here is how questions are formulated and explained over the phone. What definition of a "location-based service" is being used for example? (Pew typically posts survey questions but in this instance they're missing.) In addition, if you asked people about the importance of location on mobile devices the numbers would be far larger. And once again, frustratingly, Pew doesn't segment or break out smartphones vs. non-smartphones.
Pew does however segment LBS usage by users of Twitter and social networks. Twitter users tend to use LBS much more than other populations. This makes sense in many respects.
If the extrapolate these Pew figures (from the 4% figure above) and turn them into real numbers, we can say that there are about 8 million users of these services in the US.
People want to focus on scale and volume in these discussions. Yet talking about how many users there are today misses the larger point in a way. The larger point is that these services have brought together something interesting and relatively new, combining local-social-mobile, and created a model for a next-generation cityguide, among other things.
I had been thinking about LBS chiefly in terms of coupons and direct marketing opportunities. However these services can equally be brand engagement tools or mediums. In fact, in some ways they're more effective in that context. They can equally work as new customer acquisition platforms and as loyalty vehicles.
There's something very interesting going on with LBS and it's important to study that carefully. The market is changing and LBS is a new model for future services. Any of the individual companies may not survive but the larger phenomenon of social + local + mobile definitely will.