What he means is, say your riding a pig, you have no control over the piggie whatsoever, so he wants to dictate every move it does or else the piggie dies a slow and painful death.
I think it mentioned on the Upcoming Features page on the wiki that SOMEONE in Mojang stated an interest in adding maybe... horses? I don't remember which animal it was. But it'd still be neat to be able to use them as a faster form of transportation and would be awesome to pull hard-ass drive-by's on Skeletons and Zombies using a bow and arrows while riding a horse. That's some medieval gangter **** right there.
`EvilTrust9
What he said...