I use a large 7 inch angle grinder at work almost every day, and even went through a Kevlar glove into my knuckle at one point, not fun. However I received a similar injury on my belt sander with a 36 grit belt. Taking extra care goes a long way with any machine. Almost any injury I've received on a machine was my fault as far as I remember. Takes a lot for people to blame themselves and not the machine.
Given that info I use a 4 1/2 inch grinder to cut my blanks out. I can get about 2 eight inch blanks out of one disc. My only concern is after cutting out many blanks is that I probably have more invested in the cut off discs as I would a porta band with a couple quality blades. I'm now in the market for a porta band, not only for cost effectiveness, but also for the cleanliness of not having sparks flying around making a mess (and a fire hazard).
Ultimately, don't be afraid of an angle grinder being overly dangerous, most times it's operator error when it fails. People use them for their careers every day. Proper safety practices are a virtue. Always check your discs for cracks and don't try to make curved cuts that put tension on a disc. As I said before, it's a cheap way to get into cutting blanks reasonably quickly, but the investment adds up because discs can be quite costly.
My .05(inflation)
Justin