The Samsung Galaxy S8 is without a doubt the most beautiful phone I've ever seen, and while I've kept a case on about every phone I've owned, I'd want to make the S8 an exception. It's curved, glass body is one to behold.
But then again, I'm also known to drop my phone, and the latest scientific tests from SquareTrade show that the phone is super-fragile. Maybe a case is worth it.
SquareTrade sells protection plans for mobile devices, so it's not like it doesn't have an M.O. here, but the carnage in the video of the tests is enough to make anyone think twice about letting their S8 go naked. The company has changed its scoring this year, but says the S8 is far more fragile than last year's S7.
The phone's screen shattered on the first attempt to drop it on both its back and front (in fact, dropping on one side led to cracks on the other), and some glass fell off entirely. That's especially bad (and potentially dangerous) because of the software buttons. When SquareTrade dumped the S8 and S8+ in water, they both had some audio distortion afterward, but that returned to normal after half an hour.
The company gave the Galaxy S8 a breakability score of 76 and the S8+ a score of 77, declaring both devices are "medium-high risk." Both received tepid grades on repairability because of a strong adhesive holding the back panel to the phone. But once it's pried open, it's not too difficult to replace parts if you have the know-how (though the battery can be tricky).
See Tom's Guide's review of the Galaxy S8 and S8+ here.