Cisco IOS Wildcard mask
Terry Slattery CCIE#1026 (The fist one to pass a CCIE exam)[1]:
"I had to jump in on the wildcard mask topic, because the idea of inverting the subnet mask has been around since the early days of Cisco training. I asked Kirk Lougheed, one of Cisco’s founders and the principal software developer at the begining, about why the wildcard mask uses the bits it does (i.e. 1 = don’t care). He told me that it was just a decision he made one day and that it could have gone either way."
Scott Morris[2]:
Access Lists actually came before subnet masks. Remember way back when we lived in an evil classful world. So back in like 1985, when access-lists came about it was actually easier to code in assembler to do a NAND operation instead of an AND. Thus the wildcarding.
Francois Labreque[3]:
Access-lists and ospf areas use wildcard masks because back in the days of the AGSes, every CPU cycle counted and using a wilcard mask makes the logic of deciding if a packet matches a couple of cpu cycles faster.