Staying logged in means that you are basically sending a cookie that indicates you are logged in each time you load a page. That cookie is enough to let you make posts under your identity. So while not as bad as sending a password, it's still pretty bad - somebody can impersonate you with just the cookie.
Any machine that sees that request packet can see the cookie. That includes your ISP and anybody sniffing packets if you are using an open WiFi hotspot. Even if you just load a page from this forum while "logged in" without sending the password, you have just given somebody what they need to impersonate you. Sending a password is slightly worse, unless you reuse passwords across multiple forums - then you are really playing with fire.
The short story is that ranting about HTTPS seems to be uninformed. We're not going to break old machines and browsers. But we will encourage people to do their normal activities here using SSL to minimize the risk. And everybody should understand what the risk is and mitigate it properly.