Loopt, a mobile mapping/social networking service that lets you and your friends keep track of each other, has scored Verizon Wireless as its latest - and thus far greatest - customer.

According to Silicon Alley Insider, the start-up still has a host of hurdles to jump before it can claim success. First, there needs to be a lot more folks with GPS-enabled phones since that's a Loopt requirement. Second, it might want to reconsider its planned $4-a-month fee, especially if it's targeting the teen crowd that might be willing to pay for downloadable content but might not want to shell out the extra cash for a social network when so many free ones exist. Third, the article points out that Loopt might not work across carrier networks, so if you have Sprint and your friends use Verizon, you'll need a different way to find them.