What could cause two different iphones to incorrectly show my address as their location? Two different people have come my door today looking for their lost iPhone. Both seem to show the exact same location, the middle of my backyard. Both said they lost an iphone 5, one on tmobile, the other on sprint. Besides being annoying, it got me thinking - What could cause this?
Pure guess, but …

The geomapping for the local WiFi connections is incorrect.
Somebody recently moved house &amp; took their router with them, or bought one from someone else, etc, etc &amp; the locations database has not been updated to reflect this.  

Find my iPhone relies on already 'knowing' the position of all available WiFi APs [irrespective of whether or not it can or has ever connected to them] to triangulate the current location.

See How Google-and everyone else-gets Wi-Fi location data for a background story.
&amp; HT5467 Updating WiFi router location in Apple's database? for some ramblings on what happens when the database doesn't get updated.

As far as a guess on why two different people had the same issue, that has me stumped, unless the 'owner' of the out-of-position WiFi is also the source of the vanishing phones.