Although a developer may have success in the short term with a high ranking site by using ‘Black Hat’ techniques, it will soon drop. When discovered a search engine will take action against a website using unethical techniques to boost its rankings. They will more than likely remove the whole website from their index. Being removed will cause a lot of harm to a company even a brand opening the doors to all their competition.
When you think that Google take 48% approximately of all web search queries, being removed would be very detrimental to a company’s marketing efforts.
You can read more about deceptive techniques to avoid at Google’s Webmaster Help Centre: