There’s a great Google Webmaster Help thread about a sketchy SEO firm. You know firms like this, ones that promise “first place in Google search results guaranteed”.
Ok there are dozens (hundreds?) of firms that promise results like this. The problem is that these sketchy “black hat” SEO tactics can work for a while. Truthfully, you may see great results from these shysters for six months or so until you trip an circuit breaker in the algorithm and your website disappears from the Search Results entirely.
Anyone making grand promises or quick results should be avoided. Going down this path is like gambling, the allure of a getting a quick and easy return can suck you in, but ultimately the results can be devastating.
The Google Webmaster Help thread is particularly entertaining, because one of these sketchy companies gets outed by Google’s spam master, Matt Cutts. Barry Swartz of Search Engine Roundtable covers the discussion here.