I do a lot of kerfing in my work. In half inch thick stock (poplar), I kerf 7/16" deep, and never have a problem with strength. However, the bends I'm making are fairly severe. I think making slight bends is more difficult because conventional wisdom says the slighter the bend, the further apart the kerfs can be. If you draw a circle in SketchUp and zoom in on it, you'll find you don't have a circle at all - just a series of straight lines. The more segments you put into the circle, the smoother the curve. Same thing with wood. If you spread your kerfs wide apart, you'll get several straight segments that "curve" only at the kerf locations. To get a smooth curve you need the kerfs close together - something you may not want to do for a slight bend.
"A lot of people are afraid of heights. Not me, I'm afraid of widths."
-Steven Wright.