Poor User Experience: Make it easy for the user to get around. Too many ads and making it too difficult for people to find content they’re looking for will only increase your bounce rate. If you know your bounce rate it will help determine other information about your site. For example, if it’s 80 percent or higher and you have content on your website, chances are something is wrong.
Often the line between pay per click advertising and paid inclusion is debatable. Some have lobbied for any paid listings to be labeled as an advertisement, while defenders insist they are not actually ads since the webmasters do not control the content of the listing, its ranking, or even whether it is shown to any users. Another advantage of paid inclusion is that it allows site owners to specify particular schedules for crawling pages. In the general case, one has no control as to when their page will be crawled or added to a search engine index. Paid inclusion proves to be particularly useful for cases where pages are dynamically generated and frequently modified.