The BBC signed a technology deal with Adobe last year. It enabled the BBC to make their iPlayer Mac-compatible. Replacing Microsoft's WMV and RealSoftware's proprietary formats by Flash Embedded video doubled the video views.
It's of course impossible to attribute this raise only to the Mac community. It proves that embedded Flash Video actually presents a lower threshold, enabling more viewers to take advantage of the iPlayer.
Recently, the BBC ditched Microsoft altogether and will be replacing their Microsoft-backed desktop applications by applications that are based on the Flash/Flex framework.
It's all the more an interesting development since the Dutch national television recently came under fire when they adopted Microsoft Silverlight technology to stream the European Soccer Championship.