What you're seeing is a secret hiccup in geolocation-based systems with waypoints defined by users: they're not always in the right location. Foursquare is a fine example of the problem because I can stand at any location in town and say "here, this is where Safeway is located." It then dutifully saves my current latitude / longitude and forevermore uses that, not a street address, as the basis of where that spot is located on the map.

I don't think people deliberately try to mess up the database, but I do think that sometimes people might have left a venue when they finally create it as a new point, not realizing that the point they're recording is actually a block or two away from the correct spot.

There are a couple of different ways to fix venues, depending on whether you've unlocked the "Superuser" badge in Foursquare or not, but the general solution is to use their Web site as you can't fix a location within the mobile version of the app (at least, not that I can figure out!)

I had the same issue with a local Safeway and tried a couple of different ways to fix it. Let me show you what I did, then suggest the easiest of solutions afterwards!

My first thought was to create a new point with the correct lat/long so that's what I did. I stood in the middle of the store's lot and added a new Foursquare data point called "Safeway - N. Boulder (correct latlong)". I figured that later going to the site and deleting the old and replacing it with the new, then renaming the new, would be easiest...

I logged into foursquare.com, which gave me a simple search box:

A search for "Safeway" reveals the mess of points in the database:

Notice #3 and #5 are the same place, the latter being the one with the correct location.

When I look at the wrong location venue, the problem is immediately obvious:

Looks like the point was created while someone was in their car, driving to/away from Safeway, rather than from within the parking lot or while standing within the store.

Since I'm going to mark one as a duplicate of another, I need to grab the point location number, which is easily done from the URL:

The bad Safeway? That's Foursquare location #113333. Remember that.

Now, I back up and go to the correct location:

Here I enter the #113333 value to mark the two as duplicates of the same venue. Since I have Superuser capabilities, I click on the little pencil icon while I'm here and edit the venue information to add a bit more information (It's a matter of a single search on Google to identify the street address and phone number):

When I'm done I also fix the location name and click on "Edit Venue" and it's all saved, making this a particularly informative Foursquare check in point.

Now it's up to the Foursquare folk to merge the two data points and create one that has the correct location and information, etc.

Having gone through all of this, however, I now know that an easier and more efficient strategy for this particular app is to simply drag the identification marker on the map to the correct location rather than create a duplicate point and have to merge the two. If you don't have Superuser capabilities you won't be able to do that, so it's a good reason to check in more often and unlock it, right?

There's a bigger issue here with geolocation applications and games, of course: how do you fix bad location markers? Hopefully competitors to Foursquare have also thought this through because I can certainly imagine that down the road it's going to be a bigger and bigger issue as more and more points are added to the database...