Grief Miners of the same faction.

[Kireiray]

If you see someone of the same faction mining, walk up to it and mine as well. It seems to work out that if they are not casting when you finish your mining cast, you can steal some of their ore. This looks to have been changed in a recent patch, since you used to not be able to touch the mine at all for a few seconds after another player mined it.

[Zore.]

Hum interesting rep if comfirmed

[ihatelag]

No, you're wrong, You could always do this. I used to do this all the time after some asshat did it to me. 6):

Just for clarity, you do mean something like this, right?

Player one, mines. You run up while their cast is done.
Right after you think they've looted, cast mining.
@#$@Profit?@#$#

[Someonecool]

No no. It works like a chest.
The mining animation denotes a player opening the node or 'chest'.
When the loot window comes up, you can't start a new channel until it's has been looted or closed.

So to prevent getting your ore ninjaed you have to NOT loot the mine until you're ready to quickly start mining again.
And if you want to ninja someones ore, you have to start your channel right after he has looted and then NOT loot until the guy is gone.

EDIT: BONUS INFO
As a paladin you can cast Blessing of Protection on a miner, that will stop his channel and you can ninja your (his6) ore.

[Kireiray]

Ah, from my experience I thought I had made an accurate assumptions of how the mechanics worked. Sorry about that, and thanks for clarifying, Someonecool.

[Thorodin]

Someonecool, this doesn't work anymore, since 3 or 4 patchs...
verify your informations before giving them,please

[Someonecool]

Thorodin: it does work exactly like that. Just now I got a friend to log on and verify it with me. So thanks for making us spend 10 mins and miss an AV queue.

[Soloninja101]

gawd i hate when ppl did that to me!!