Why? There's no qualitative computational difference between a smartphone and a desktop computer; further, the quantitative difference between today's smartphones and older Flash-capable machines of a decade ago is probably not that huge.
Absolutely not true that there's no difference. The speed of your desktop comes from using POWER. Today's desktop CPUs alone pull up to 130 WATTS. My desktop CPU bought in 2000 used 30 W. Now even notebook CPUs use more when they're not idle!
Now I can come to a lot of web pages where only Flash ads use 100% of a modern CPU! That translates in 60-70 Watts.
Then compare all this with the goals for device which should work with battery for hours.
Running flash content on a PC bought around 2003 is actually pretty choppy. I installed Windows 7 on an old Athlon 1.6 ghz machine a month ago and tried to watch youtube with it -- the videos looked like they were going around 8 fps. I can watch old divx movies on it, but I can't watch youtube full screen... it's pretty sad.
This machine was fast enough to play Quake 3 and a dozen other gaming titles, but is too slow to play youtube videos. I just don't get it, is the flash vm really that processor intensive?
I can't see how flash could run well on the upcoming android devices if it runs so poorly on the Athlon 1.6ghz.
Newer Flash Videos codecs like H.264 probably are that intensive. Codecs have changed over the years, giving us better quality, but also requiring hardware support or lots of go juice to run well.
I don't mean to suggest that it should run smoothly on any of today's smartphones (though some N900 users commented that it runs well for them). I just take issue with the "nearly impossible" in the parent of my original comment. But I suppose I may have interpreted that to mean more than was intended.