Recently I was thinking about how websites like gmail and amazon use HTTPS during the login process when accessing your account. This makes sense, obviously, since you're typing in your account username and password and you would want that to be secure. However, on Facebook, among countless other websites, their logins are done with simple HTTP. Doesn't that mean that my login name and password are completely unencrypted? Which, even worse, means that all those people who login to their facebooks (or similar sites) at a wifi hotspot in public are susceptible to anyone getting their credentials using a simple packet sniffer (or something similar)? Is it really that easy? Or am I misunderstanding internet security?

I'm a software engineer working on some web related stuff, and although at the current time I'm not too involved with the security aspect of our software, I knew I should probably know the answer to this question, since it's extremely fundamental to website security.

Thanks!