Last year, Google unveiled the revolutionary idea of infinitely customizable maps, maps that might look different depending on your tastes, your friends (and their tastes), your Web history and your previous clicks. "A map for every person and place," the company called its updated Google Maps. And it promised a digital map so personalized that it would learn about us the more we used it, anticipating our preferences for mid-priced Indian food, or dive bars over Irish pubs, or bike lanes to get there.

The idea offered a radical departure from the old static map, the interpretation of one cartographer given to everyone. But its promise of personalization raised some awkward philosophical questions: What happens when we don't have a common view of the world? What happens when the city I see is different from the city you see, or when the Internet decides for you what you don't need to see? Couldn't customized maps kill the serendipity that makes bustling, chaotic cities special, or -- worse -- reinforce the biases that we already have before we even walk out the door?

Increasingly, we can move through the Internet following only the people we agree with, reading only the media outlets that mirror our views, finding only the Web sites meant for our demographics or politics or purchasing patterns. A digital map that narrows our view of the real world around us invites us to have a similar experience there, too. If I don't see that bodega online when I'm searching for grocery stores, I won't see it in real life, either. In fact, I may think I live in the kind of city that has no bodegas at all.

All of this is pretty abstract. It's stuff for academics or cartographic theorists. But last week, we got a pretty good example of how customizable maps might in fact reinforce biases in a problematic way, not at the local level but on a geopolitical scale. Below are two maps of Crimea, the territory claimed by both Ukraine and Russia, the one at left viewed through the U.S. version of Google Maps, the one at right seen through the Russian equivalent:

Google Maps

In Google Maps parlance, as several savvy media outlets have noticed, the dotted line refers to a disputed border, the solid black line to a definitive one. To further complicate matters, this is the version of the map you see when you're in Ukraine (or on

Google Maps

There's no border at all other than the one that separates individual regions within the same country. Google is clearly in a tough spot here, waging into the geography of conflict. And you have to imagine that Russian officials might be upset with the tech giant if the local version of the map looked any different.

But from a consumer perspective, it's easy to imagine how these maps might create a false sense of consensus on disputed borders. If you live in Russia and you think Crimea now belongs to the motherland, this map tells you that you're right. Maybe you think it's telling you that the world agrees with you. Quite literally, it's giving you a different version of reality than the one other people see on this same plot of land.

The problem of mapping disputed borders isn't a new one, or even a product of the Internet age. But this particular scenario brings us back to the original question, which has relevance at all scales, whether in your neighborhood, your city, your country or your part of the world: If the map I see is different from the one you do, how are we going to agree on what we're looking at -- or even know that we're not looking at the same thing?