If a non techie user surfs a website and the latter one horribly slows down his "device", in the most common case, and specially if the website is "famous", this user will blame its wonderful piece of technology, rather than the infamous designer/developer that created the problem.
This happened recently, as example, in Hotamail and with the latest Sherlock Holmes Flash banner.
The Solution Is SimpleStarting with the fact that Junior Flash developers are as responsible as advertisement hosts, unable to filter proper banners from annoying one, if a company would like to provide these heavy computation banners it should simply make a little investment as a whatever Atom CPU based device is (even just an all in one motherboard is enough!).
Even better, it could recycle a generic good old Pentium III based PC in order to be sure that computation is reasonable, where for reasonable I mean no more than 50% as maximum peak.
As an old ActionScript developer, I've always found disturbing the fact people paid to create ads, are too often unaware of problems they could cause.
I have already commented here or elsewhere old Tiscali or IBM heavy banners, recently improved and much less painful for low cost CPUs, I still find ridiculous that in 2010, the beginning of the mobile and low power consumption era, a good movie as Sherlock Holmes is could be sponsored in such obtrusive way: obtrusive for nowadays net dedicated devices: please change it!