If you collect any information or data at all from your users--which you do just by having a website (traffic logs are kept whether you use them or not)--then you need to have a privacy policy. You need to give some thought to what you are collecting, and what you will and will not do with it. This may include more than your own website(s); for example, Facebook pages collect extensive usage and demographic information.

Barrie North at JoomlaShack.com has helpfully pointed out this simple form that will generate your policy for you based on the boxes you check in answer to various questions. Thanks also to the Direct Marketing Association for offering this helpful tutorial and policy generator.