When I'm tanking I'll stay in the tank no matter what, if I'm the driver I mean. If I'm against a tank and I don't have one of my own, I'll run at it (regardless of my kit) in the hope that I don't get killed and harass the driver into hopping out, I watch the minimap and as soon as the tank turns white I tap E to get in even if the tank is burning. I try to make sure they have no chance of repairing it and getting back to the fight, even if that means I have to kill myself, because it leaves them with a long walk home at least!
I'd say 75% of the time I get killed by the tank, 10% I'll persuade the driver to leave, hop in and then get team killed because it was burning out from friendly damage, 5% of the time I'll hop in and the enemy will kill me but that last 10% I'll get in, kill the driver and drive away, keep that tank for quite some time and make good use of it. I'm relatively decent when it comes to tanks but rarely choose to take one of my own team's, I much prefer taking theirs! Same goes for scout choppers.
Also once I chased a tank into the Siene, much to the amusement of my squadmates. I was an assault, too; no C4 or anything that could do any real damage. I had been going for a steal but he just kept reversing into, then through, the wall and into the river.