That was the same sell for Flex during it's 1.0 days. Silverlight, at it's core, is truly targeting Flash; however with the understanding that Rich Internet Applications can also be browser based too is first, then second that Flex outputs a *.swf just like Flash does.

So Silverlight will go after one or the other and Flex doesn't have the mindshare of Flash since it just requires the Flash plugin and that's all the end-user knows/sees.

Marketing at it's best. Go after what people know the best.

I will go on record to say that Silverlight Mobile, from what I've seen is just as tight as SVG-T. And that's impressive to me... but not enough to fully endorse it in most of my upcoming projects.