C4 persistence -- does it depend on where you plant it?

I am almost positive C4 has the same rules as mines. On the ground, they will stay there until they are blown up / triggered. Although, when you place C4 on vehicles and then die, you are correct: The game will remove those items. I assume they set that up so players cannot camp enemy vehicle spawns through lives.

EDIT

C4 will no longer be detonable after a player respawns, if the player is revived within 5 seconds he can still detonate his C4.

As apart of the patch notes released on March 27 See here for more info.

C4 does not behave the same as the tank mines. If you plant C4 and die, the C4 is removed. Perhaps there was a coincidental explosion at a time that made you believe that your C4 had persisted?

Here is the link from Dec 11:

http://www.battlefieldhq.net/index.php?option=com_content&view=category&layout=blog&id=60&Itemid=361

Fact: C4 will persist on vehicles after you die.

New fact: This will change with the next patch.