The issue is even worse. Some sites are embedding login to remote websites. Here, for example, you've used disqus for visitor comments, which may require us to login from your own site. Now, can you please tell me how to make sure this is the real disqus login form and not a fake?
Also, please note that sites such as facebook do require secure login, but after that transfer the users to plain HTTP site, which allow man in the middle to grab our session cookies and use our identity. This is what FireSheep demonstrated recently.