It seems like we just barely finished putting the ISS all together, and already the Russians have decided that by 2020, the whole thing is going to be deliberately crashed into the ocean. Wonderful.
The ISS has actually been up there and manned in one form or another for going on 11 years now, which means that despite the fact that the last several pieces (more or less) of the structure just showed up relatively recently, the useful life of the station has already passed middle age.
The original schedule for the ISS assumed that the entire thing would be completed by 2003, but (stop me if you've heard this one) the project ended up running nearly a decade behind and was (is) vastly over budget. But at least we've got it up there now, which is the important thing. President Obama has already extended the lifespan of the ISS from 2016 to 2020, and while theoretically the station could keep on going until 2028 (after which component lifetimes start to become an issue and accumulating micrometeorite damage gets to be a problem), at this point, 2020 seems to be the cut-off date.
Since the U.S. is legally obligated to maintain responsibility for anything it puts into orbit, something has to happen to all of our ISS modules, and since bringing them all home would have required 27 separate missions flown by a now-decommissioned space shuttle, all we can really do is just deorbit everything into the ocean and hope it doesn't land on any whales. The Russians, on the other hand, are already planning to refurbish many of their ISS modules and reuse them as part of a new Orbital Piloted Assembly and Experiment Complex (OPSEK) to support deep space exploration.
Via Discovery News