Paid inclusion
Also known as: pay per inclusion(ppi)
Paid inclusion is a principle in which search engines charge websites a fee to be included in search results. The payment can be either a flat fee or an amount per click or impression.
A well-known way of paid inclusion is advertising in search engines through sponsored search results. The most popular example of this is advertising through Google Adwords. This is a fairly accepted form for search engines to generate revenue.
There are also search engines that charge money to include sites in organic results, whether for a one-time fee per page or an amount per click. Yahoo is one search engine that has experimented with this in the past. Critics say it is unfair to users if economic motives play a role in "independent" organic results. This is the reason why this model is little used in practice.
