Your point is right, but should we make compromises because they need to push commercials on videos? Do we really need to use GPU because flash is slowing down CPU and eating ram? Do we really need multiple instances flash based commercials on webpages? And tell me, why in the world Vimeo and Youtube are both offering video-tag fallbacks to their players but only for mobile users?

Yes, I'm ranting because I've seen during the past 5 years an abuse of the flash platform. And I see the same today with web-based video services. Now we are facing a web where 99% of video players are flash based.

Thousands of macs users are blaming it because it's damn slow, so we are looking for alternatives, but we can't have them because of advertising? Is this serious?

Browsers developers are going faster than light, developing new versions every two weeks, javascript engines are always better, unratified tools are included on all A-grade browsers. We have all the tools. We can do that. If we desperately need to push advertising, well, we'll find a way. We will make a virtue of necessity.

So, as you said web developers must be concerned to deliver their best design, and to me, best design means not only happy clients but also happy user.