rooting - Is it possible to completely brick your Android phone by using a Custom ROM?

I understand that you can completely "brick" (render unusuable) your iPhone by attempting to Jailbreak incorrectly.

Whether or not this is actually the case, is it possible to do the same with your Android phone? Or is the nature of that operating system and the handsets such that you can always install a new ROM on it if everything goes pear-shaped?

I assume there could be a difference due to how closely the iPhone is tied to iTunes, compared to how independent Android phones seem.