It look like a simple trick to deceive people from visiting a website but actually its a tactic wherein you have to have someone who knows to read Google Algorithm and what should be done for your website to make it better. Advertising on other people's website is what other people do to make their certain product be known all through out the web. One of the biggest advertising company is Google itself, second was Bing/Yahoo, and the 3rd now was Facebook. How come that Facebook became an Advertiser? Now look at your right side bars and if you see the SPONSORED at the top of the malicious posts that is an advertisement.
Earning in the Internet is much easier before due to low SEO compensation. SEO before is not yet that popular but when 2012 came in Google started to make the software that killed a lot of websites which is called the Google Penguin. But it did not ended there yet, they also created another one which is called the Google Panda. Those killed a lot of business and had prolonged the life of others who are worthy for their post.
Of course Other SEO Marketers know some sort of a way to earn money that is by Blocking Download links by showing you a survey. When you finished the survey that's the time that they earn money. They are really smart to think some sort of a way to earn money by doing those kinds of tricks.
There is also an incident where in a Business website went missing after becoming #1 in Google for 10 years. They said that they are liable of what they have done. They created a website to Advertise their products using a software to create a 1 thousand word content article which is a very great thing for a website to be on top. Others are said to be using Black Hat and Grey Hat SEO which is known to be destructive to other websites.
SEO has a lot of things under its sleeve, but by somehow having someone who knows to progress in the internet is actually in a very slow process. I don't think buying backlinks to other people is a great Idea either sure it will drove a lot of traffic but too much would kill your website.
That's all for now