First vendors start releasing things with SD card readers, and people quickly realise Linux can't use them. Then several very talented hackers start a project <http://mmc.drzeus.cx/wiki/Linux/Drivers/sdhci> to reverse engineer SDHCI controllers, since the SD Card Association won't release specs publically (apparently citing "trade secrets").
Talented hackers get things working so well that it makes it into 2.6.17-rc1 <http://www.kernel.org/git/gitweb.cgi?p=linux/kernel/git/torvalds/linux-2.6.git;a=history;h=6246b6128bbe34d0752f119cf7c5111c85fe481d;f=drivers/mmc/sdhci.c>.
After all this is done, the SD Card Assosociation, seemingly without any prior communication, release a simplified spec http://www.sdcard.org/HostController/index.html> now that the community has figured it out.
Of course it acts as a good check that what was reverse engineered is correct, and reverse engineering things can certainly be a lot of fun. But really, what a lot of wasted resources thanks to a backwards vendor. What exactly have the SD Card Association gained, apart from bad will?