It's not about https
The always interesting LastKnight's blog (written - in italian - by Matteo G.P.Flora) raised the silly question you, as a nerd, heard so many times:
"I can't trust online-shopping: I don't want to use my credit card over the Net! What do you think 'bout that?" [normally the question is raised by elderly relatives or non-tech-savy friends]
This is the good answer by Bruce Schneier, quoted by LastKnight.
"What you’re really asking me is about the security. No one steals credit card numbers one-by-one, by eavesdropping on the Internet connection. They’re all stolen in blocks of a million by hacking the back-end database. It doesn’t matter if you bought something over the Internet, by phone, by mail, or in person — you’re equally vulnerable."