Fast givaways on game that are free for a limited time.

I don't know....but I'm SCARED!!!!! D:

They'll get blacklisted by many people.

You can't make giveaways less than an hour in duration.

Do people like that get punished in some way?

Not really but they won't get CV neither.

It's not allowed to make giveaways for free keys while the keys are still being given out for free. So most likely they'll get a temporary suspension as they are mass reported by the users.
If they're hoarding keys now and waiting a couple of days before giving them out again, they won't be punished though. In either case, they won't get CV.