Using a technology (ie. plugins) that lists the incoming search terms of past visitors to your blog pages is a bad idea and I shall go over a few reasons.
You would not send your marketing plans and tactics over to your competitors but having the search terms used to find your pages, is giving them plenty ammunition to get their site ranking as high or higher than your site if you have these posted at the bottom of your articles.
If you are running AdSense, for example, certain keywords on the page could block the advertisement from showing and accidental and deliberate search terms by visitors (ie. your competitor) could stick on your pages causing you loss revenue.
After a while, Search Engines are going to treat this as spam as it is not adding any value to the reader. As a matter of fact, Search Engines has started to encrypt their Search Results and will delete the referral keywords used to find your blog’s page. Only Google Analytics will have the information if you added it to your pages and SEO spammers will taint it with fake referral spam.
So, do you see how potentially bad it is? Good! Check out tips for new bloggers and Happy blogging!