I have had two WordPress blogs hacked into in the past. That was at a time when I was doing very little internet marketing, and until I found time to address the situation (months later), these sites were penalised in the search engines. They were not removed, but the rankings were reduced.
Install the fix hacked wordpress site Firewall Plugin. This plugin investigates net requests with simple heuristics to identify and quit most obvious attacks.
Do not depend on your Web host - Many people rely on their web host to"do all that technical stuff for me", not realizing that sometimesthey don't! Far better to have the responsibility lie with you, instead of out of your control.
I don't think there's a person out there that after learning just how much of a problem WordPress hacking is that it is a good idea to boost the safety of their blogs. However is that when it comes to securing their sites, bloggers seem to be stuck in this state that is reactive.
Along with adding a secret key to your wp-config.php document, also consider changing your user password to something that's strong and unique. WordPress will let you know the strength of your password, but include amounts, use letters, and a great tip is to avoid common phrases. It's also a good idea to change your password regularly - say once every six months.
Don't use wp_. Web hosting providers are eliminating that default but if yours does not, fix Source wp_ to anything but that.