A study conducted by security software company Sophos has shown that Microsoft's search engine Bing is more likely than any other search engine to show results related to spam or malware infected websites, due to its vulnerability to engine poisoning attacks.
Search engine poisoning attacks are a form of black hat search engine optimization that attempt to skew results so that malicious websites such as those with malware or deliberately misleading fake versions of actual websites appear prominently in the index of sites related to popular search terms, sometimes even higher than legitimate websites.
Sophos' research division, SophosLabs conducted the study, by monitoring how many of their users were blocked from being redirected from a search engine to a malicious website. 65% of the poisoned search results blocked by Sophos over the two week period originated from Bing while 30% came from Google. The other 5% came from alternative search engines.
Obviously, these raw statistics do not account for the fact that Google is by far the most popular search engine so the numbers may actually be far worse.
According to Sophos, 92% of malicious redirects were related to image searches.