Here's one that even we could've predicted--before coffee: tiny cars don't fare well in accidents.
Like one of those scientific studies that are obvious, foregone conclusions but someone has to conduct them anyway just to get everything on paper (e.g. "Does jogging make you sweat?"), the friendly folks at the Insurance Institute for Highway Safety played smash-up with a handful of minicars. In the ring, they pitted brother against brother: a Honda Accord versus a Fit, a Mercedes C class versus a Smart Fortwo, and a Toyota Camry versus a Yaris. And what did they find? "[V]ery small cars generally can't protect people in crashes as well as bigger, heavier models." Parallel tests revealed that Skittles do not taste like rainbows, breathing makes you live, and drinking gasoline is bad for you.
On a serious note, it's important to point out that the IIHS took it easy on the minicar segment, using only those cars with good crash test ratings and pairing them with mid-sized cars rather than full-sized vehicles or--ouch--big rigs. Also important to note, as IIHS president Adrian Lund points out: although many buyers opt for minicars for their fuel-efficiency, buyers can often get higher mpgs (and better safety ratings) with a mid-sized hybrid. Hint
Finally, for those who refuse to believe anything that's not in video format, here's a clip with Lund, who'll walk you through some of the study's finer points. Among his awesome (though scripted) soundbites, you'll find this gem: "Although all cars have gotten much safer in recent years, you can't repeal the laws of physics." Word.