So why do people check in? Is it, as Gowalla’s Andy Ellwood jokingly suggested, because “I am in my 20s and you should just care where I am”? Or are the reasons more substantial?

This afternoon’s panel on location-based services focused on why and how users engage with LBS (check-ins).

Gillian Heltai of comScore said the firm’s research data show that most consumers are either comfortable or at worst ambivalent about disclosing their location on services like Facebook, Foursquare and Gowalla.

The comScore survey showed that 44 percent of consumers want to know where their friends are, while 37 percent were comfortable disclosing their own location. A minority were opposed to doing so.

Heltai said that when you project out smartphone penetration three years (when we are expected to reach 50 percent penetration), there is the potential for 87 million mobile social users by 2013.

She said use of location-based services will be “driven by device proliferation and the availability of content.”

She said current data show that check-in services (Facebook Places) today are used heavily by younger males (63 percent aged 18-34 and 60 percent male).

Gowalla’s Ellwood said the reason consumers use check-ins and social media in general is because people like to “tell stories about their lives.” That may be a bit self-involved, but it is more substantial than the running cliche about tweeting that you just put grape jelly on your toast.

So checking in at a restaurant, pub or charity event helps advance that personal narrative. Check-ins at more mundane stops (the dry cleaner) are much less common.

Ellwood talked about how Gowalla is working with some very well-known brands to leverage the check-in phenomenon to engage with customers and build their brands.

One example is the Sundance Film Festival, which is using Gowalla to help solve the problem many festival goers suffer — an experience overload that leads to a rather sketchy memory of what they did at the festival.

So Gowalla built a program that allows Sundancers to check in at every screening party and receive a stamp that will leave a digital trail of what they did at the festival.