Why are Intel Macs so picky with RAM? I remember back in the PPC days PC ram will work on a Mac even if it is not certified to work on a Mac.
Today, it's hit or miss with non-certified RAM modules.
I always thought Macs wholly ran on commodity PC hardware.
You can use any good quality RAM modules that meet the spec of that particular Macintosh. If you buy from a place that sells rubbish, then don't expect it to work. If you buy RAM that doesn't meet the specs of your Mac, then don't expect it to work.
If you buy from one of many reliable sellers, and make sure that you buy the right RAM, you'll be fine. You can save lots of money by buying from a reliable seller instead of buying from Apple directly (or from Dell, HP etc. directly, it's the same principle). That's what I do, and never had problems. You can save a tiny little more by buying from unreliable sellers who sell unreliable memory. Not worth it.