That's the point. It's empirical (albeit, not scientific) evidence that even when presented with the risks, users will still choose to do things that are dangerous.
dan·ger·ous
[deyn-jer-uhs, deynj-ruhs]
–adjective
1. full of danger or risk; causing danger; perilous; risky; hazardous; unsafe.
2. able or likely to cause physical injury
This behavior extends beyond Internet usage. I (and probably most of you reading this) hand my credit/debit cards over to waiters several times per month knowing full well they could jot down enough information while out of my sight to make illegal charges on that card (if not do far worse via more elaborate identity theft schemes). Risky? Yes, but the extreme convenience outweighs the potential pain due to the low chance of actually being one of the people that gets exploited in this way, and thus it is with open hotspots and most Internet sites.
I use a credit card because it's safer and offers me options - someone snarfing the number would be a nuisance, because I'd need a new card, but that's it.
Let's please not forget (Sight.. I know - everyone already has) that charge-cards were pushed onto the market as a safe, convenient alternative to using cash - not a walking liability - don't let the issuers turn them into one on us.
As to the analogy - it's quite different. I'm very security conscious, and I generally don't do certain types of activity on uncontrolled or unknown networks (banking - home or somewhere else safe - but facebook at starbucks, okay)
IT's not just a problem with open hotspots, it's with any network you are on, anywhere - an open hotspot is just the easiest place for someone to try this on. An employee at an ISP could snarf data from millions of users easily...
Seems like the ones who read the message must have made a quick cost-benefit analysis in their head of viewing facebook insecurely right now versus not accessing facebook at all - and viewing it right this minute no matter how insecure still won!