As opposed to some sites having linking policies that deny people from linking to their pages, I have the reverse of such a policy: I will not link to certain sites from my pages. In fact I will only link to things that I actually approve of in one way or another, e.g. a company will only be linked if I like its products or policy or I have something important to say about it.
The reasoning behind this is this: Google, arguably the best search engine in the world, gives higher importance to sites and pages with more links pointing towards them. I am not about to link to sites I don’t like, and thus increase their score on the search engine. If you desperately want to find out about the company or product, I’m sure Google will turn up enough results to get you going.