Since starting my Foursquare research project, I found a few people using it but a lot of people with an opinion of it. People are either avid users, or avoiding it altogether.
The privacy concerns appear to center on the check-in functionality. A check-in is when users indicate via their mobile device that they are currently at a specific location/venue. Users can elect to have these check-in automatically streamed to their Facebook and Twitter accounts.
Here are some of the privacy concerns I heard from friends:
"I used to use foursquare/gowalla but stopped. The main reason is because I didn't want people to know when I wasn't home and where I was most times. I may be overreacting but I have a little girl and must think of her first."
on why she won't use it as she's "too paranoid! The Man is already tracking my every move, and I barely leave the house"
Others suggested that my Foursquare posts made me an ideal candidate for robbers (missing that if robbers removed most of our cheap Ikea furniture, semi-broken electronics, mountains of toys, Zellers-clothes, they'd be doing us a favour). There was a website set up (now closed) that gathered user data to show how easy it was for people to see who was away from their host. This discussion has already played out on the blogosphere.
There were good points against this belief, as robbers are much more likely to stake out a house to see if anyone is there or telephone the house then they are apt to constantly monitor an online feed to see when houses are vacant. There was also an assumption with a lot of this debate that people lived alone, as just because one person is out doesn't mean all of a house's occupants are.
There were also false assumptions about how much data Foursquare makes public. Unless one has been friended by another Foursquare user, they cannot ever see their check-in history. There isn't even an option to make this public. If one does a search for someone on Foursquare's website, you see their profile picture (users are encouraged to upload a picture, but a real photograph is not required), first name and last initial, city, their friends, badges, tips they wrote, usage stats, and their "to dos" (i.e. items from others users that they want to do at a speficic venue).
Foursquare let's users decide whether or not to: "Let friends see my phone number and email address; Let people see the links to my Facebook / Twitter profiles; Show my name in the 'Who's here' list when I'm checked in; Let local businesses see that I've checked-in at their venue". Many users don't change the privacy settings, but in that case I blame the users not the applications.
If one links their Twitter or Facebook accounts, then there are options to have Foursquare automatically post one's check-ins or earned badges and mayorships. I did link my Twitter and Facebook accounts. My Facebook account is closed (only friends can see anything) but my Twitter account is open. I therefore decided to not allow Foursquare to automatically tweet, but I was fine with updates going to Facebook. I realize not everyone has set up their Facebook or Twitter privacy settings, but they should!
In addition, with each individual check-in a user does, the user is given the choice of whether or not to announce their check-in to either their friends, Twitter, or Facebook. If one decides to check in but not tell their friends (called "off-the-grid") still allow the check-in to count toward mayorships and badges. I like off-the-grid check-ins when I'm checking in a lot and don't want to constantly bug my friends (people can elect to receive a pop-up on their mobile device announcing a friends' check in).
I was concerned about mayorships - as they are essentially announcing that one is frequently at that location (or else they wouldn't have been able to become mayor). If one searches for a location, they can see the name of the mayor or who authored the associated tips. I emailed Foursquare about this concern - AND THEY REPLIED. Mayorships can be declined on one's profile page of their website, by clicking the X next to the location. I understand that the value of Foursquare lies in having mayorships be publicly available so that vendors can identify frequent customers and users can identify whom they have to work against to steal the mayorship.
Foursquare does, however, need to do more to allow users to specifically target what information they want to be public. There should be settings to control what one wants to display in one's public profile, such as friends list and location. Users should also have the choice of their profile not being public but still being able to use the system.
Foursquare indicated they are revamping some of the features to improve privacy. Still, from the discussions I had with non-users it wasn't the actual privacy options of Foursquare that were that concerns, it was a misconeption of how much information was made public. I remember similar concerns that kept some people from joining LinkedIn or Facebook, so perhaps this will dissipate as people learn more about Foursquare and more will join as they'll beceome increasingly pressured to join once it (presumably) hits critical mass.