I've seen premines stolen. I can't recall which coin, but it caused a shitstorm. And of course, proved the dev was a noob and the coin was crap.
I also remember that coin (not its name though...)
![Grin](https://bitcointalk.org/Smileys/default/grin.gif)
Actually with x11 coins, I often ended with my own fork and the premine... but it never sticked
actually I don't think it is really possible to steal the premine (well unless in that previous case... and noob dev
![Grin](https://bitcointalk.org/Smileys/default/grin.gif)
).
The dev just need to kill off the seed nodes and start again and call it the "correct" fork