There are a LOT of security features here you won't find at Blogspot or other blogging sites. The #1 issue on the forums seems to be people trying to do stuff that would (as a side effect) compromise security and WordPress won't let them.
Just as some examples, WordPress doesn't allow javascript (which is how MySpace was hacked, if memory serves) or embeds other than certain types they've examined and cleared: YouTube, Google vid, Grouper, and Odeo for sound files.
I'm sure a techie could tell you a lot more than I, but I guarantee you WordPress has some pretty darn robust protections in place. It may mean we can't run some groovy stuff in our sidebars, but that's a small price to pay for knowing your blog will be there when you wake up in the morning.