Gray Hat Marketing

This type of marketing is semi-ethical/unethical SEO in nature. It was also said that you may face penalties using such SEO but you'll not be banned. How it will be known if you're using Gray Hat marketing? And what would be the penalties one may face if he was caught?

Gray hat marketing lies between white hat marketing and black hat marketing. Here, the site owner provides greater risks than white hat marketing, by disobeying to some of the search engine guidelines, but at the same time ensures limited disobedience so as not to fail into black hat marketing. For example, gray hat marketing may involve a keyword density higher than required but not too excessive.

I guess sandbox may be one of the penalties!!! Not sure though!! ???

Sandbox? How would that be possible then?

I guess I have enough information about Gray Hat Marketing. Thanks for all the responses. I appreciate it a lot.