Snooping websites, which do you ban

Been monitoring my stats with Woopra and just recently started to notice one or two snooping web sites showing up for hits.

When you click on the links fot the hits they have such titles as

"check your competitors keywords and top search queries, log in here" type pages.

Its a bit disconcerting knowing that others are trying to hit on the success from your own hard work, ie track what brings in the most hits, then try and go one better.

Is anyone else suffering from this type of thing and what are you doing to stop this.

Are there any know sites to ban or ip´s to try and stop accessing your forums?

Thanks in advance
Lee

It is going to be almost impossible to stop it.