Like Bill Gates used to say 640k is enough for everyone (although he never said such a thing, but that is a different discussion), I only need seven buttons to pwn

.
But seriously, I only use buttons 1-7 on my hotbar and use SHIFT+1-4 to switch quickly through the different bars. This is because I find the other keys hard to reach. Also, 6 and 7 are always mapped to lifetap and fear respectively.