I haven't been disturbed in RP by any hackers atall, and I consider myself lucky, as quite alot of people I know have encountered them, and I can understand why it would be so immersion spoiling to encounter them. The devs do promise to include a good anti cheat system, which I hope will be thorough and strict.
Bad Roleplayers are, in my opinion, the biggest threat to Identity. The game relies on the community to make it what it is, and without a good community, the game is literally useless. I have to agree with Johnny here:
Also, keeping the game at a high price may filter out the unwanted guests. After all, trolls will not go as far as paying £30 to annoy people.
As for twelvies, I am unsure. I have met alot of people of the age of twelve or just above or just below that are nice people, but even though they are nice people, they are immature, and will not grasp or engage in the concept of the game properly. It's quite a difficult situation go deal with, because we don't want to be massively segregative, but we also don't want to ruin the RP experience, so, like Johnny said, a whitelist with a thorough test is in order. Maybe not for the official servers, but definately for the community hardcore RP servers.