The most important feature for finding Pokemon in Pokemon Go is broken. In order to locate Pokemon in Pokemon Go, many trainers use the Nearby window, which shows how close nearby Pokemon are to your location. Each Pokemon's distance away is represented by 0-3 paw prints, which allow players to get their bearings and use the function to find nearby Pokemon.
At some point yesterday, the Nearby tracker went down and all nearby Pokemon now appear with three paw prints underneath them, even if they're much closer. The problem appears to be tied to the Google Maps API, as the maps that show you where you caught a Pokemon (found by tapping a Pokemon in the "Pokemon" menu) have been replaced with a blank white screen.
The Nearby tracker isn't entirely broken, though. When opening up the tracker, the Pokemon in the upper left hand corner of the box is the Pokemon closest to your location. If another Pokemon moves in front of the Pokemon you're looking for, you're moving in the wrong direction.
There is no current known fix for this bug and it appears to have affected all Pokemon Go players, regardless of location or device.
It's likely that Niantic is aware of the Nearby tracker and is working on a fix, but players are still encouraged to report the bug to make sure it's a priority item. This is likely a temporary problem that should be resolved soon. Hopefully, everyone will be back to rushing out of their home when a rare Pokemon is one footprint away soon.