We’re talking here about Adobe Flex/Air rather than about Silverlight, it is generally because we’re working with Adobe products now. But it’s nececary to find out also different ways of creating RIA applications and this way can be a Silverlight, so read some interesting article about it. I found Serge Jespers (Adobe platform evangelist) review of his Silverlight training course and this is maybe you should read.

Read His article.