It’s the internet equivalent of snake oil, astrology or political promises. Pure nonsense, but enough people keep falling for it that it’s worth running the same scam over and over.
As Keeve has pointed out, the word ‘guarantee’ doesn’t mean much in this context. It’s just a word they put in the ads to give people a false sense of security. You give them some money, and they do something or other that they think will help your search engine rankings. If it happens to ‘work’, they keep your money, and if it doesn’t then most people won’t bother to ask for a refund.
Those that do try to get their money back will experience long delays and endless excuses. ‘We never received your email’, ‘Can you just send the details once more’, ‘We can’t give a refund without a return code’, ‘We can’t issue a return code unless you have your refund number’, and so on. Plus the company may just go out of business, or change its contact details, or claim that your claim is being processed when it isn’t.
What of the actual ‘service’ these people provide? It’s plainly nonsense. What if two customers both wanted to be top search result for ‘car rental’? They can’t both be top, can they? And who determines what being ‘top’ means… does it mean for one minute, one week, one month, forever… or what? Maybe you and the company will have different ideas about this.
Most of these companies will do nothing except explain to you what meta tags are and how to use them (information you can get for free all over the internet), and then try to create lots of fake links to your site that use those tag words. This may fool some search engines, some of the time, but the search engine people aren’t idiots and they are constantly waging war on these tactics. If they find you are using lots of fake links to drive traffic, they will take steps to either ban you or at least nullify any benefit.
One point worth bearing in mind is that most of these companies advertise their services using a rather subtle bit of misdirection. Suppose they say they can prove their service works. They might mention a site they have worked on that is all about, for example, car rentals in some specific region. They will show you that if you enter ‘car rental’ in Google, the specific site they mentioned is top of the rankings. But this misses the point. It’s easy to win this game if you get to choose the exact search terms, but in real life you don’t. In real life, people might enter any of the following (bear in mind that many people don’t know how to use search engines very well):
rentals car
car for rental
renting car
want rent car
rent a car
hire cars
cars for hire
where hire car?
cars, hiring
Avis
and so on… and perhaps there’s a different ‘top site’ for every permutation. I’m pretty sure I could get any website to be ‘number 1’, so long as I had control over how everyone uses Google and which search terms they use.
I run a successful commercial website, and for over ten years it has generated enough money for me to live on. Here’s the best advice: offer a good product or service. Work hard to get your first few customers, and let word of mouth do the rest. Don’t worry too much about Google rankings. Worry about offering something worthwhile, dealing fairly, and giving your customers a reason to recommend you.