Any personally-identifiable information such as email addresses and user names must be mentioned in the policy. You may be collecting this information without really knowing it – most WordPress blogs, for example, allow anyone to register with the blog as a subscriber. Technically, this information collection must be mentioned in the policy.
Eric Giguere is a writer and software developer who has written extensively about computing and technology. Be sure to read his other articles for more interesting information on a wide variety of topics.