Do Not Link

Did you know that when you link to a website, regardless of the reason, this strengthens its position in search engines? It's not a bad thing when you are promoting something, but if you are warning users against something it can be more harmful than helpful!

This is where http://www.donotlink.com/ can help: you can freely link to the site without worrying about increasing it's prevalence in search engines! They even make it easy to use it without visiting their site every time:
http://www.donotlink.com/www.example.com/shady/stuff.html

So the next time you post warning folks away from it, use donotlink.

Note: if you are blogging on Blogger, Google also has a way to do this.