Flash is a poor example because the majority of consumer PCs sold already include a reasonably recent version of Flash. This is why I'm still building adgames in Flash when I'd much rather use Unity3d. Unity adds the friction of a plugin install, whereas Flash is likely already installed.
Similarly, getting people to install Chrome Frame adds some friction (though how much depends on how the install is streamlined).
I'm not sure I'm with you here. A lot of offices have really old computers purchased around the time of Windows XP SP1 and the version of flash shipped on those will leave quite a lot to be desired.
So maybe I should have said it's like saying IE (in those types of settings, anyway) doesn't support new flash games because they don't have the right version of the plugin :)
Similarly, getting people to install Chrome Frame adds some friction (though how much depends on how the install is streamlined).