SAN FRANCISCO — As more people reveal their whereabouts on social networks, a new site has sprung up to remind you that letting everyone know where you are — and, by extension, where you're not — could leave you vulnerable to those with less-than-friendly intentions. The site's name says it all: Please Rob Me.

Launched last week, Please Rob Me is exceptionally straightforward. Pretty much all it does is show posts that appear on Twitter from a location-sharing service, Foursquare. Please Rob Me puts these posts into a long, chronological list it refers to as "Recent Empty Homes."

Please Rob Me assembles its list by taking information that Twitter makes freely available so that many Web sites can show tweets. But the point of Please Rob Me could be made with data that flows on dozens of other sites as well.

People are comfortable sharing all kinds of personal details on social sites such as Facebook. And now people are flocking to location-based Web services, such as Foursquare, Gowalla or Loopt, that let them use their cell phones to alert friends to where they are.

Some people choose to show their whereabouts only to approved buddies. But plenty push these very specific updates through public Twitter profiles that anyone can see.

This phenomenon is what motivated the creators of Please Rob Me, according to one of them, Boy Van Amstel, 25. Van Amstel said in a phone interview from Holland, where the site is based, that technology has become so easy to use that people are sharing too much online without even realizing it. He and his co-founders want people to think twice about it.

To drive the point home, Please Rob Me's Web page shows a scruffy-looking, loot-lugging burglar. Below that, it indicates that the site is "listing all those empty homes out there."

It doesn't really show empty houses, or even people's home addresses. Instead the posts on the list show Twitter users' photos, their Twitter usernames, how long ago they "left home" (which is determined by when they checked in with Foursquare) and where they went, along with a link to their destination on Foursquare's Web site.

Foursquare co-founder Dennis Crowley said he can imagine that sharing where you are could have bad consequences. But he said it hasn't come back to haunt him and isn't something Foursquare has heard complaints about.

Indeed, there doesn't appear to be any evidence that saying you're not home on Foursquare, Twitter, Facebook or a similar site significantly increases your chance of becoming a burglary victim. FBI spokesman Jason Pack said his organization's cyber division wasn't aware of any cases of home break-ins linked to people advertising their locations online.

After all, there are many ways, including low-tech ones, to determine that someone isn't home. Pack said burglaries are usually crimes of opportunity — that is, they're often not planned in detail.

Regardless, Kevin Bankston, a senior staff attorney at the Electronic Frontier Foundation who focuses on privacy, said the message of Please Rob Me is still important.

"There is clearly a privacy issue here — one they are trying to shed light on," he said.