graeme_p - 7:43 am on Sep 27, 2013 (gmt 0)
The Searchmetrics study is utterly meaningless. A key rule in statistics is that "correlation does not imply causation".
In this case, all they have proved is that sites with lots of ads are low ranking sites: it does not prove that they rank low because they have lots of ads. It may be that sites that have lots of ads are MFAs with terrible content, it may be that people are reluctant to link to sites with lots of ads, it may be that site owners are more willing to risk having lots of ads on low ranking sites, it may be that some sites or some forms of advertising, or some ad layouts are penalised and not others, it may be that the top ranked sites for many keywords are not for profit or have a business model (e.g. selling their own stuff) that does not require ads. Most likely it is a combination of all of the above, and good luck guessing what matters for a particular site.
That said, if the site looks dominated by ads, its generally not a good thing.