While Google never sells better web ranking position in our search engine results, a number of other search engines combine pay per click or pay-for-inclusion results with their normal web search ranking results. Some SEOs will promise high ranking in search engine results, but place you in the advertising section instead of in the search results. A few SEOs may even alter their bid prices in real time to create the illusion that they “control” other search engines and can position themselves in the slot of their choice. This scam doesn’t work with Google because our advertising is clearly labeled and separated from our search results, but be sure to ask any SEO you’re considering which fees go for permanent inclusion and which apply toward temporary advertising.
Do you know the most typical abuses a website owner is likely to encounter?
One typical scam is the creation of “shadow” domains that funnel users to a site by utilizing deceptive redirects. These shadow domains often will be owned by the SEO who claims to be working on a client’s behalf. However, if the relationship sours, the SEO may position the domain to another site, or even to a competitor’s domain. In the event that occurs, the client has paid to build up a competing site owned entirely by the SEO.
Another illicit practice would be to place “doorway” pages packed with keywords on the client’s site somewhere. The SEO promises this will make the page more relevant for much more queries. This is inherently false since individual pages are rarely relevant for a wide range of keywords. More insidious, however, is that these doorway pages often contain concealed links to the SEO’s other clients as well. These doorway pages drain away the link popularity of a site and route it to the SEO and its other clients, which might include sites with unsavory or illegal content.
What are a few other things to look out for?
There are some warning signs that you may be dealing with a rogue SEO. It is not a complete list, so if you have any doubts, you should believe in your instincts. By all means, feel free to leave if the SEO:
* owns shadow domains
* puts links to their other clients on doorway pages
* offers to sell keywords in the address bar
* doesn’t distinguish between actual search results and ads that show up on search results pages
* guarantees ranking, but only on obscure, long keyword phrases you would get anyway
* operates with multiple aliases or falsified WHOIS info
* gets traffic from “fake” search engines, spyware, or scumware
* has had domains taken off Google’s index or is not itself listed in Google
Article from Google : Search Engine Optimization SEO