The reason I say this is because of the Adsense and Adword programs Google offers. When you use the Adword program to promote your web site your ads will not only appear on the Google result pages but also on web pages that joined the Adsense program. Even better on Web pages that have the same focus as your web site has. Your ads will be shown many times on the internet when you have set a high budget in Adsense. The ads that are shown however are not only ads they are links too!
Now when the crawlers of Google spider a website they must find the Adwords links and count them for ranking. So the higher the budget, the more links, the higher the ranking, the higher in the search results will be.
Is this true? This theory requires some investigation because this could help in the common SEO practice.
First of all I examined the ranking of all the first Adsense ads I found on web pages. The Page Rank of these pages was very different varying from 0 thru 4. So it looked as if Adwords doesn't help you getting a higher ranking. So I had to look deeper to find the answer. Looking at the source of the pages where the Adsense ads were on I was astonished to see that the ads were written in JavaScript. It is a well-known fact that the Google crawlers have a hard time spidering links in JavaScript.
My guess is they have chosen this solution to prevent the spidering of the Adword ads.
I have to say that this is an honest method because content is king. The best site with only quality links in will be in the top of the search results. So buying a top position in the search results is not possible. On the other hand buying an top position in the Adsense results is and this will be on the same page....