Something that needs to be repeated from time-to-time.

Deceptive advertising is so common one might get the idea that is okay or effective.

Of course it can be effective in the short term. "There's a sucker born every minute" is all too true. Outside of the moral and ethical issues involved, it is not effective in the long term. Eventually bad word-of-mouth, lawsuits, etc. etc. catch up with you.