Last month, as part of the SSL rollout, Blogger added a page / post / template editor feature - that not everybody understands. A blog with "HTTPS Redirect" enabled will provide SSL access, for every reader - both those who intentionally use HTTPS, and those who normally use classic "HTTP". Those who normally use "HTTP" will find themselves redirected to "HTTPS" - no choice. When you use page editor, post editor, or template editor, on a blog which offers "HTTPS" to everybody, you may see an alarming alert.
What Blogger won't tell you