I know where you are, good buddy

GPS receiver not required
Even if you don't have a GPS receiver in your phone — as the new iPhone and many other new phones do — you can still take advantage of many location-based services, such as social networking using your mobile.

Federal law requires that all cell phones have E911, or "Enhanced" 911, which allows emergency personnel to find your location.

"The E911 obligation allowed carriers to choose one of two solutions," said Farren of CTIA. "One solution involves having a GPS chip in the phone; the other is network-based, which is triangulating the three closest cell towers to a call to provide the longitude and latitude."

Verizon Wireless, Sprint and Alltel use a GPS chip in their phones, he said; AT&T Wireless and T-Mobile rely on triangulation.

If you're considering trying a mobile networking program, be sure to read the company's privacy policy, which most programs discuss or link to prominently on their Web sites.

Even Loopt, based in Mountain View, Calif., and highly regarded, had a privacy blooper last month when it launched its program for the iPhone.

Brightkite After getting requests from users, Brightkite added additional privacy controls that "make sure your privacy is set to the proper mode at sensitive locations."

Some iPhone users who downloaded the free program said Loopt sent text message invitations to contacts listed in their iPhone address book, which created a lot of unwelcome messaging, as well as cost.

Company president Sam Altman, in an interview with Information Week, said the glitch may have happened because the user interface was confusing.

Loopt explained the goof and apologized to users in a blog posting on the company's site.

"If a user clicked the 'Who's on Loopt button,' we checked his or her phone book for other Loopt users. The mistake we made was automatically selecting them, so if the user then hit Send, they might inadvertently send more invites than they meant to. We immediately disabled that feature. We don't store your contact list, and it should go without saying we would never sell it or share it with a third party."

Within days, Loopt asked users to download a fix to its software.

Whrrl, owned by Seattle-based Pelago, Inc., shows users not only where their friends are at the moment, but also where they have been, and their thoughts about those places. The company notes on its blog, "Whrrl will only update and share your location upon request ... Location updates are only broadcast to people in your People Who Can See My Location list, which you control at all times."

Brightkite, makers of a similar program, recently received some requests from users for options to be able to go off the radar at specific locations. The company changed its software so that users can mark locations as "Always Private" or "Always Public."

The ability to make these kinds of decisions is important when considering using such a program.

Subscribers "should look for the option to hide their location details and only disclose it at their desire, and also make sure that they have the ability to opt out any time they feel their privacy is being compromised," wrote Karthikeyan in the Current Analysis report.

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