I came across this very interesting interview with a former adware programmer. In his early days, Matt Knox designed and wrote adware for a company called Direct Revenue, which would later be sued for allegedly installing adware on millions of computers. The irony came from the fact that Knox was recruited while working on spam filtering software. Initially tasked with troubleshooting their ad distribution chain, he eventually graduated to direct work on the adware. When quizzed about the strategies used to maintain the persistency of the adware he worked on, Knox answered: "Most adware targets Internet Explorer (IE) users because obviously they're the biggest share of the market. In addition, they tend to be the less-savvy chunk of the market. If you're using IE, then either you don't care or you don't know about all the vulnerabilities that IE has."
Knox went on to elaborate on a common strategy - tapping IE's Browser Helper Object (BHO) for nefarious purposes.
So if you are ever looking for a reason not to use Internet Browser, this would be it: Microsoft's Internet Explorer is the preferred attack vector for adware - and presumably other forms of malware. Of course, Internet Explorer has made tremendous improvements over the years, with Internet Explorer 8 touted as one of the most secure yet.
However, one can also argue that Beta 2 of Internet Explorer 8 scores a dismal 21 percent on the grueling ACID3 browser compliance test, compared against the much higher scores from Mozilla's Firefox, Opera and Safari, to name a few.
Of course, a non-Microsoft browser is certainly no guarantee of immunity against malware of any form. However, given a chance to pre-emptively nip a swath of security problems with IE in the bud, would you take it? Or rather, can you afford not to?