What makes a website look legitimate? Is it the design and style? Is it the content? Is it the links to and from the site? This question is very subjective, because for many Internet surfers, "legitimacy" of a website is based on his or her preferences. Some people may feel that a site is more legitimate if it offers no advertising, and others may feel the opposite, for example.
A recent thread at WebMasterWorld Forums links to an interesting study published by Harvard and Berkley scholars titled "Why Phishing Works." The WMW member relates this to AdSense as follows:
It is sometimes a concern that putting ads on a (legitimate!) site will reduce the perceived quality of a site--that somehow the site has been hijacked by the webmaster who wants to make a quick buck. (Whereas we're innocently just monetizing our websites, of course!) But this research seems to indicate that with careful page design and intelligent use of ads, the perceived authenticity or authority of our page content may actually increase.
Whether or not the Phishing paper can be related to this topic is questioned, but I feel it is an important snapshot of some people's views of websites. A few members share what they feel makes a site look legitimate. I personally do not get offended or impressed by sites that host AdSense, Yahoo! Publisher Network, or any other sort of static ads. I do get a little perturbed when pop-ups or pop-unders come into play, however. I can smell a Made-For-AdSense (read more about MFA's) site within seconds of entering, and usually microseconds later I am elsewhere (*unless of course I am fishing for some good overused content- just kidding)
Hopefully some more opinions on this subject will find their way into the thread soon at WebMasterWorld Forums.