The key here is not just in what you say, but more importantly what you do not say. I do not advocate lying, but you do not need to confess all your sins to your clients, either.
I believe that any time there is a potential conflict of interest or perception of undue bias in my writing, I want to disclose it so you can decide how big of a grain of salt to take with my ramblings.
Thinking about going into business for yourself? Check out my list of the Top 15 Myths About Business in the Business Articles section of this site.