Anybody with any sort of website needs to think about security. If nothing else, a hacked site is embarrassing.
Part of keeping your site secure is keeping the software up to date, just like you do with your own computer (I hope). There is a constant battle going on between nice people improving and fixing software and nasty people trying to find new holes which they can exploit for their own gain. The nice people are working for your benefit so take advantage of their labours and use the upgrades they provide.
If you have a self-hosted WordPress Blog, like this one, then you need to be aware of a new attack. Take a look at Lorelle on WordPress for details. If you haven’t upgraded to WordPress 2.8.4 then your blog is vulnerable to this attack.
We have already upgraded all the blogs we host, we keep an eye on software upgrades as a matter of course. WordPress is very easy to keep up to date, some other packages require a lot more work, but we will always apply security fixes to any package we host.
No system is 100% secure but by keeping up to date you encourage those nasty people to look for easier targets.