Do you really trust this giant browsing program you are running right now? How big is it? How many lines of source code are involved? Have you vetted it? Did the authors find all the security flaws in it? Did it come from berkeley? Does it use X? involve X? Do you really trust people from Illinois to get it THAT right? Remember, it is probably running as you, and has access to all your files, all your stuff.
Does it call other programs on your system? Of course it does! Do you trust them, too?
Remember, the Internet is a Bad Neighborhood, with subway stops in all the seediest parts.
Here's a follow-up quiz. Click here to detect a possible flaw in your browser or operating system.