Why is Internet Explorer unsafe?

See what people are saying about Internet Explorer, in the wake of its most recent security issues:

New York Times, In Search of a Browser That Banishes Clutter:

Ms. Sandlin is so devoted to [Firefox] that she has taped a note to her monitor warning guests not to click on the desktop shortcut to Internet Explorer. Do not touch the blue ‘E!’ the note says.

USA Today, Security risks swell for Microsoft’s Explorer:

Using Microsoft’s Internet Explorer Web browser to surf the Internet has become a marked risk — even with the latest security patches installed.

The Inquirer, US Government warns against Internet Explorer:

The US Government has sent out a warning out to internet users through its Computer Emergency Readiness Team (US-CERT), pleading users to stop using Microsoft’s Internet Explorer.

eWeek, Bugs, Exploits Dog XP SP2:

Meanwhile, security researchers are reporting a new vulnerability in SP2 that could allow a malicious Web site to deposit an attack program on a user's system. The attack utilizes Internet Explorer's drag-and-drop features and the Windows "shell folders" to copy an executable From a malicious Web site to a user's startup folder, From which it would execute the next time the user logged on.

Slate, Are the Browser Wars Back?:

[A]ll-conquering Internet Explorer has been stuck in the mud for the past year, as Microsoft stopped delivering new versions. The company now rolls out only an occasional fix as part of its Windows updates. Gates and company won the browser war, so why keep fighting it? The problem is that hackers continue to find and exploit security holes in Explorer.