Better passive cooling on a HD4850
Contrary to your suggestion, it is not impossible to get very good passive cooling on a HD4850. Gigabyte could, for example, have sourced a decent passive cooler like the Arctic Cooling Accelero S1 instead of designing their own rubbish one.
I installed an S1 on a stock Radeon card and subjectively it seems to run pretty cool, but these guys have actually run the tests: http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/8299-sapphire-radeon-hd4850-512mb-graphics-card-review-24.html
Not everyone will fancy voiding their warranty by doing it themselves, so it would be nice if a company would do it for us instead of going down the bespoke route...