Keep in mind that IE, as the most used web browser in the world, will necessarily attract the most bad guys trying to find holes in it to use as means to do bad things to people surfing the web. When Gecko-based browsers increase significantly in usership, you will see an increase in security vulnerabilities in those browsers. Why? Well, if I am a hacker, then I want to hack as many people as possible with a single attack vector...
IE has certainly had its share of security blunders, but consider what IE does: it enables users to surf aimlessly in the dangerous waters of the Internet. It is necessarily on the front lines when it comes to facing Internet-based attack, because it is an Internet explorer, after all. It is not at all surprising to me. This is exactly why security is the most important focus for IE right now. It simply has to be.
You want a 100% secure browser, 100% secure operating system, 100% secure Internet? Well, then don't connect to the Internet. That said, in the future this will not necessarily be the case as users will have become more educated and systems made more secure, but the sad fact remains: there will always be bad people out there working tirelessly to figure out ways to hurt as many people as possible, even if only in abstract or virtual ways.