I just managed to reset my Yahoo password, knowing only my username, date of birth, country, zip code, and my father's middle name. No hacking necessary. If I can do it, someone else can do it too.

All of that is stuff that can be easily obtained by someone who knows me.

I'd recommend using some safer solution for e-mail. (I don't use Yahoo for mail myself, but Flickr requires a Yahoo ID). Or answering wrong to those stupid "safety" questions (in a way you can remember).

Also, your username and password probably have been compromised by something much more common than WiFi eavesdropping. Maybe your PC has a keylogger trojan. Or some other place you've been accessing your mailbox at.

Or maybe you've typed your username and password to a website after clicking a link in e-mail you just received. And that happened to be a phishing site. (Almost happened to me once, with some very authentic looking FB notification. I only noticed the trick, wrong URL on the address bar, because the e-mail field was pre-filled with some strange address.)

Unfortunately, https won't protect any of the above.