There's only been one generation of Windows Phone with two releases.

Windows Mobile was substantially different and went through many generations with upgrades dependent upon carrier implementation.

True from Microsoft's perspective but from a customer's perspective it looks like "Windows for phones" changes radically and entirely incompatibly pretty often.

Edit: On the other hand, most of the current market probably didn't know about Windows Mobile so perhaps that's mostly moot.

Twice in the past 10 years, or once every 5 years. That's the difference between iOS 1 (2007) and iOS 5.

We could just as easily say "twice in 2 years, or once every year" since the first WP7 devices shipped in late 2010 and WP8 will be out by end of 2012.

That's ignoring the long history of Windows Mobile from 2002 to 2010 though.

That history is irrelevant since we're talking about Windows Phone and not Windows Mobile.

Did HN get over-run by MS employees or something? What the hell is going on! :)

WP6 > KIN > WP7 > WP8. I count three killed platforms in three years.

Kin wasn't an official Windows Mobile/Phone platform, though.