Benefits of Facebook Places
Most Options on Facebook places are active by default. So whatever functionality you do not want, you have to opt-out yourself. You can either opt-out from Facebook Places completely or optimise the privacy settings to suite your privacy needs. Facebook Places is available for the iPhone as well as Smartphones with support for geolocation and HTML 5. Facebook Places is currently available to Facebook users in the US.
The major concern for Facebook users is the possibility of their location falling in the wrong hands. Stalking is a common occurrence on Facebook; location information means that the stalker will know where you are currently. Not only that, he will also know where you have been e.g. where you shop, the club you go to, etc, information that easily enable him create a more detailed profile about you than have previously been possible.
However it is not only stalkers that you should worry about, it is about your location falling into wrong hands. Imagine burglars using your location on Facebook Places to know that you are out of town and using the opportunity to rob your house while you are away. Note that Facebook applications can also access your location if you allow them to. So Facebook Places has a number of benefits, but there are a lot of privacy concerns some of which may simply be hot air, but a number of them are real. Hence you need to think carefully before leaving your Facebook privacy settings untouched. Here is an article about customising your Facebook settings for Facebook Places.