Maybe for tourist travel it's a cool way to spot old historic buildings you'd otherwise not find, but for real estate? I would expect that whatever real estate catalogue you browse will also list the build year. As another commenter said, that data is in public databases (called the "kadaster"), I would assume every real estate agent is aware and uses the kadaster-data :)
Which doesn't detract from the fact that this is a beautiful visualisation. And also I doubt the general public can query those data in the bulk amounts required for this map :)
I'm one of the designers at funda (largest Dutch real estate listing site) -- though on the Personalisation team and not the Search or Presentation teams.
This is definitely a beautiful and useful visualisation and something we've been thinking about for a while too. We've found that in an average real estate search people very much appreciate information about the neighbourhoods they come across when finding relevant properties. The thing I love about this is -- like some others pointed out already about Rotterdam -- is that it tells a genuine story about a neighbourhoods history in a way a real estate agent wouldn't be able too.
In the US there's Trulia Hindsight built by Stamen Design which includes animation: http://hindsight.trulia.com
I think are way too many errors in the data set for that. For example, you might end up at Hoog Catahrijne shopping mall, listed as being from 1893, built in 1976, and in the process of a huge overhaul.
True, the big academic hospital here is coloured as really old, but the shape of the building is definitely mostly modern additions, parts of which I've seen being built while I lived here :)
But to properly display that is a real hard problem. First, you need way more data, a complete history of the changing shapes of buildings as they were being reconstructed/renewed/etc, over the ages. Second, how to visualize all of that? Layer all of it on top of eachother, with old at the bottom and newer shapes covering it, maybe? or ... stacked in 3D, like a geo/archeological excavation!
Right now it seems a bit of a compromise, mashing up two datasets that don't always properly "fit" together. But on the whole, on average, and for many aesthetic purposes, it does a very good job.
The catalogue will list the build-year of the property you're looking at, but will it give much information on the build-years of the other nearby buildings?
Which doesn't detract from the fact that this is a beautiful visualisation. And also I doubt the general public can query those data in the bulk amounts required for this map :)