Low Trust for Search Engine Ads?

According to a study by Nielsen Co. (via SEW blog) only 34% of consumers trust search engine ads. That puts it right above banner ads and just below ads before movies. This brings up a lot of interesting questions. I don't have time to explore all of them, but I wonder how accurately you can really measure trust? Or do we really care about trust if customers are buying products? I mean, SEM almost always gets much better results in terms of conversion rate and cost per conversion than Radio, TV, Sponsorships, movie ads, newspapers...so do they really trust those media more, or do they just think so when asked the question in a survey? Or do they buy from a search ad even though they don't really trust the site? If so, I'd rather have the sale than their trust. (For the record, I think you need their trust to get the sale). Also, I assume whey they say 'search engine ad' they're referring to the paid ads, not organic results. Where would these people rank the organic listings in terms of trustworthiness?