You could also have incoming links with those mispelled keywords as anchor. Im always surprise whn I look a Google keyword suggestions. I sometimes find some mispelled keywords with heavy monthly search and competition between advertiser is next to none. With adwords, this is cheap and almost guaranteed traffic.
No, Google will not banned you and I think even if it is a misspelled trademark Google will not banned you as long as the misspelled keyword is present in your page thus making it relevant to your site.
They will not ban you, but when someone does a search with the misspelled word then Google would provide the web user a suggested corrected spelling, hence "Did you mean _ _ _ _ _ ?" This inadvertenly will lessen your CTR for the misspelled word, but its worth a shot or at least doing some research and analysis to see if it works for you.
They can't ban you if you have or own the domain of the misspelled ones. Well, that's what I thought, but I'm not a lawyer. I think this problem is bigger than just banned and not banned. Some companies are taking legal actions for these kinds of matter. If I can remember correct Microsoft is suing people using their name in the domain (whether good or bad).