Enderman cannot teleport from a minecart (this may be exclusive to moving minecarts, I don't know). This is true even if the enderman is taking damage from water/rain. I think the teleportation sound was playing but the enderman did not leave the cart.
Not my video, but shows what I am talking about: http://www.youtube.com/watch?v=WI6jWk_ozH8#t=12m00s
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yes i have seen this it turns red an sometimes vanishes for a second but is always intsantly teleported back to the minecart. im no modder but it makes me wonder if the player/mob stays in the minecart because he/she/it is constantly being teleported into it
Added cats and dogs.
I think this should stay this way.

Is this still a concern in the latest Minecraft version 14w04b? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
Confirmed in 14w04b.

Confirmed for Enderman for
14w30c
14w31a
Minecraft 1.8-pre 1
when outside the worldborder (it seems like they are teleporting, but they aren't really which you can see because the enderman is still sitting while teleporting and also dies at the position of the minecart)

Confirmed for 1.8.
They also do not pay.
😞

Endermen however teleport for a short moment away from the Minecart but then re-appear in it in 15w51b
That's a separate issue.
Can confirm.