An online friend was asking me this question the other day. Selling in house advertisements and text ads is a good way to earn revenue for your online properties. Be aware though that Google has stated they are penalizing paid links since 2007 but as long as you do it right and that you know what you’re talking about in your paid reviews, things should be fine.
Most people are worried that selling paid links might affect their Google Pagerank, but if you have good numbers of backlinks and good contents, I don’t think that your site traffic will be affected much just because you’re selling paid links. Yeah, pagerank might be affected a little, but do you really care and control that? At the end of the day, think of your site visitors first and accept ONLY links and reviews which are relevant for your site visitors.
Advertising revenue is simply the lifestream of online sites (same for magazine and newspaper) and if I have to choose which between pagerank and advertising revenue to sacrifice, I will choose pagerank.
Simple decision, eh?