Hi Nicky,
IMHO SWF was an important part of the web in its early days as many things were not possible without it. But with the implementation of basic HTML5 by modern browsers this has changed: the <video> and <audio> elements allow playing multimedia files in more open formats than Sorenson Spark or VP6. And the <canvas> element even allows arbitrary animations, which can be programmed with Javascript. So I see not much use for SWF nowadays, except as fallback for older browsers. After all: HTML5 and Javascript (to be exact: ECMA script) are international standards, opposed to SWF which is proprietary software.
Nicky wrote:On the other hand, YouTube still offers all their video's in .swf.
Youtube offers an HTML5 video player since more than two years:
http://www.youtube.com/html5. And I'm sure this will be the default player sometimes.
Christoph