I've only come across them in the context of having the back of my neck scraped at the barbers, but what Joe says is exactly what I'd expect, for reasons which are gone into at great length here:
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The too long; didn't read version is that a DE blade combines a greatly reduced cutting angle and a comparatively rough edge, making it a very efficient shaving tool, but also potentially a harsh one which may well bite you. I find the idea a bit scary, frankly.