Web development or search engine optimization sites do not often speak ill of the online companies that promise you top ranking in Google or other search engines. The reason is simple. It is not because most of these companies do their job well, it is because these companies appear in ads in the aforementioned sites' pages. Why would they want to keep those clicks from rolling? Well, I am not going to do that.
Most of the online companies that promise you top ranking are crooks. They have this impulse to separate you from your money. It is not that some of them will not affect your ranking. They will...but, most probably, in a negative way. There are many categories of traffic building cheats that have different ways of “improving” your ranking.
Some rely on pyramid schemes of link building. For example you provide some links and then you have to recommend the service to other sites. If the other sites link back you gain more link credits. This massive affiliate interlinking does not work at best and may harm your site at worse. Most of these links will be from totally irrelevant sites to yous, thus gaining you no extra ranking in Google. Also Google does not particularly love massive interlinking and on top of that some of these sites might be on Google's black list dragging you down with them.
Another cheat scheme is the promise of thousands upon thousands redirected hits from “targeted traffic”. What these people do? Well, they simply own many domains and when a user hits that domain they redirect this user to you. They promise you that the traffic is targeted and that these users were aiming at watching a subject relevant to yours. Even if that is the case, these users will not stay in your site and the reason is simple. They did not expect to see your site so they presumes (correctly) that something fishy is going on and leave. It is very bad traffic at best. Hell, I have been crooked this way and I am not ashamed to say it. During “my early days” I was promised that with 36 $ I was going to have a traffic of 10000 unique visitors in a month. I said “why not, it is not very expensive, lets give it a try”. The outcome: there goes 36 dollars I am never going to see again. The company, on the administrative software that it provided for “my campaign”, was saying that I was indeed visited by 10000 unique visitors. Google analytics said around 4000. It is not the numeric difference that is bad (which shows that the company was simply lying) but that out of these 4000 “unique visitors” all simply left the site as soon as the page was loaded(0 minutes average time on site according to Google analytics). Very,very bad traffic. Who would you have me believe? the crooks or Google? As a matter of fact I still have doubts whether these were real users and not simply generated hits from different IPs.
Another popular scheme is the “pay us your good money and we will rank get you in the top 10 results on Google for keywords of your selection.” What they do not tell you, is that they will either use all your keywords as a single keyword or some other derivatives or misspellings of your keywords. The result is that your site may come out high in results but only for an obscure, ten-irrelevant-words keyword that nobody searches for.
Here is a list of things to be careful with according to Google. Look out for “SEO” or traffic companies that:
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 appear in search results
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 removed from Google's index or is not itself listed in Google
