My next door neighbor is selling her house. Being nosy, we, of course, looked up the listing. Yikes. The house is larger than ours on an even proportionately larger lot yet is listed for way below our city property tax assessment value. A number we thought was conservative.
We were in shock. Then we were angry. And after that, rational thought kicked in.
We don't plan on selling our house any time soon (as in, we'd have to be dead for the house to be sold). Our house is still worth way more than we paid for it originally (we bought when property values in our area were in the dumper also). We don't have a mortgage (no worries about a lender wanting us to pay the difference). And there is always the consideration that the newly listed neighbor's house might, just might sell for over asking (that is a small hope).
But we are taking action. We're talking to the city to have our house reassessed, using the neighbor's listing as "proof." If our property value is tanking, we might as well have the (very) small benefit of having our property taxes reduced also.