WYSIWYG editors dummy down the user experience. Users don't know how to use HTML anymore. WYSIWYG editors also makes the content one publishes harder to control. Instead of the user deciding which HTML elements to be, the editor does it instead. This has the effect of making the content less semantic. What if the user wishes to use <em> instead of <i>, <strong> instead of <b>, <del> instead of <s>, and <ins> instead of <u>? Sometimes these editors don't insert <p> tags where the user intended. WYSIWYG editors are a major facet of the Web 2.0 cancer.
This is very similar to the web after the launch of social networking sites like MySpace. Before 2001 the only way to make webpage was learn some code yourself or hire a developer.