Basically, if you're for example in a 4x4 tower with a 2x2 hole inside and a minecart 5th layer outside going spiral arround up the tower and you leave the minecart, it will throw you THROUGH the wall (it's not transparent blocks) and drop you into the air and eventually killing you.
I had minecarts popping me out inside of lava and water.
MC-40454
Leaving a Minecart Issues
Resolved
Duplicate
0
DDCA567
(Unassigned)
Unconfirmed
death, minecart, minecarts, walls
Minecraft 1.7.1, Minecraft 1.7.2
Retrieved
Duplicate of MC-36482 - If you have not , please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.