I have tried "link locking" websites in the past and they have never really proven to be useful. Unless you are willing your day spamming forums to promote warez it isn't really going to pay off.
Although this is not exactly relevant to your question, are you sure that there is no other way to monetize that traffic? You could offer them surveys, develop a popular facebook page (which can be used to advertise products and your other websites), build a newsletter list, etc. You should research these options before (possibly) risking the reputation of your websites.