Maybe because tracking down the address for a Jesse W. in SanFrancisco isn't that hard (you just need the right website), and after that... Somebody already pointed out that a "Burglar Me Please" app would be banal to write: you just walk along SF, and the app will tell you which owner is home and which is away, and how far s/he is; correlate with Facebook (is he married? is he so young he might be sharing his flat?) and you get a list of easy targets in the area.

It's not only about where you are, it's also about where you are not at any given time.

I agree. Broadcasting your location is only dangerous if you are in a potential position of danger. The fact that you are at work in a secure office building (presumably at Square) means you are probably not in a position of danger. Also, you probably don't worry about being followed home from work. If a young woman were broadcasting which shortcut down the alley she tends to take on her way home from work, one might argue that is a different story. You are not vulnerable at your location; some people might accidentally publish a trend of vulnerable locations.

One reason is that it's not just your location that's the issue.

It's your location + all the other public information I can potentially find out about you combined with your location. The combination of a lot of separate facts can, together, potentially make people open to risks that aren't immediately obvious.

For example consider what location from foursquare + sexual orientation from facebook + photo from twitter would give to the scum who gay bash. The combination of religion + location + face is another thing some folk wouldn't want to be public.

I hate to think what the National Front would have done with a "gays, muslims & jews near me" app...

People don’t think about privacy issues because our psychology doesn’t trigger much emotion for autonomous opt-in broadcast to people not currently visible. There’s no sense of violation. It’s very easy to forget about it and it starts to feel normal. In a way it’s also empowering to be so open; it makes you feel like you’re not afraid of anything.

If you actually step through what is happening when you use these apps (all the individual people you are informing of where you are and have been, your habits, preferences—a complete digital record) you might start to see some risks. Then ask yourself, even if it was easy, would you go round handing out that data on paper to large groups of contacts indiscriminately on a regular basis indefinitely? That’s what’s actually happening here. Now remember there are people (trolls) who get a kick out of being able to do things to do from a safe distance for no reason at all. There are also people closer to you who have fragile egos or maybe you were just in the wrong place at the wrong time. Using something like Foursquare is giving these people ammunition. The fantasy we like to believe is that everyone we know is trustworthy. The reality is not so rosy.

Or just doesn't want to share yet-more data to a marketing company.