The thing about spikes, is that they seem more sensitive than any type of block. I mean, it's like Samus doesn't even have to fully touch the spike tile to get hurt/knocked back. Plus, you can hit them from the side, which is stupid. They're obviously not sharp on the sides. Or wait...are they?
I always considered spike blocks in Super Metroid to be unintentionally hilarious. Unless they're "moving" then they can't hurt you. I guess Samus' suit can stand up to non-moving spikes, but once those spikes start to bounce up and down, oh no! Although I'm not talking about ones wherein people just forget to set the FX1 to make them move; just in the reg. game.