Of interest to me:
He [Sam Altman, Loopt co-founder and CEO] set out to give Loopt strict rules to prevent misuse. The most significant is that cellphone users who sign up can make their whereabouts available only to a network of friends who also buy the service.
I guess that's a safety feature, but aren't some crimes committed by friends and relatives? Moreover, isn't that also a marketing ploy, so they don't just get you to buy in, but also your "circle?"