By definition a blackhat is someone who uses hidden text techniques or cloacking in order to create doorways and rank better. A doorway is a page with stuffed keywords without any meaning for a human reader, but valued by certain search engines.
But how about those who create web pages on domains like
"buy-cheap-medicine-health-now.com" and put some copy pasted content from other pages. They create 30 such sites and start submitting them to directories and doing link exchanges. They pretend to be white hat, but are they trully? They have no idea about the subjects in their sites and they don't bring any new content for the Internet. They create those pages with the only purpose of having traffic in order to monetize it. So I consider this last category black hats too.
A true whitehat never creates new pages and domains about subjects he don't have any idea about. He only promotes his existing sites with unique and useful content, not just affiliate links and google adsense on them.