Two conspicuous absences in the abilities of Windows Phone 7 are Flash and Silverlight — the latter especially, as it is developed by Microsoft themselves. TechRadar talked to Microsoft’s Andy Lees, president of the mobile communications division, on the issue, and this is what he had to say:
“It’s not a religious thing; we support standard H.264 video in the browser. We’re not allergic to Flash, we’re not allergic to Silverlight, we’re not allergic to HTML5 – but this [Windows Phone 7 browser] doesn’t support it. We don’t have the extensibility model inside the browser for those pieces and when you see the future I think you’ll understand why.
“There is no ActiveX plug-in extensibility because of the security model; we’re not going to do that. And with no ActiveX plug-in model, how would we do Flash?”
It’s about stability, security, and battery life, it seems. Pretty much exactly what Apple said about why they don’t support Flash on the iPhone.