I wouldn't derive any particular benefit from FourSquare if I used it, as my movement from place to place is fairly routine and predictable. However, I don't think there would really be any drawbacks if you, me, or anyone else was simply GPS-tagged and stuck in a public-queriable database.

Think about this: whenever you go out in public, there are people you don't know all around you watching everything you do, and any of them could choose to stalk you in the literal, physical sense, following you from place to place without your knowledge. Putting your location online just helps people that already care about you to find you; it doesn't increase the probability that someone who doesn't care will arbitrarily start caring (in either a beneficial or malicious sense.)

Internet location publishing just makes getting information more convenient. Nothing that was previously impossible is now possible; the barrier to entry for some things (like stalking) has just been lowered, so that people can do it without investing their whole day in casually hiding in a crowd nearby you.