Originally Posted by AlexBell
...So far as I know only Kindle Touch and Kindle Fire readers read azw3, and I agree that that's a limited number of devices. But I don't think that necessarily means that only a limited number of people read azw3 ebooks...
The various "Kindle for ..." reader apps also now support KF8. Still, a substantial majority of the installed devices and apps today (2012-05) don't support KF8 and these probably never will. It will be quite some time before Classic MOBI fades into a minor player.
You should also consider that the vast majority of users, unlike the population here at MR, will not understand the difference between Classic MOBI and KF8 and thus giving them a choice will only be confusing. You should post single hybrid files leaving the user with only two choices; ePub and Kindle/MOBI.