I haven't heard of anything like this happening in Europe yet, but apparently it's becoming commonplace in the US to charge around $29 for a window or aisle seat on domestic flights and $59 on international flights.
So are we going to see rows of empty window and aisle seats on flights because passengers aren't prepared to pay extra for them? And what happens when a passenger complains that he can't sleep because somebody with a window seat doesn't have the window shutter closed? I've had that happen to me on an Emirates flight from Dubai to Bangkok last year. At the time, I wanted to get some shots of the sunrise as we flew over India, but was forced to close the shutter instead. If I'd have paid for window seat I'd have demanded a refund.
I like a window seat on daytime flights, but on night flights I don't really care that much since there's nothing much to see anyway.
More on the story here: Airlines now charge extra for window or aisle seat