If its easy and annoying then there does not need to be a motivation. Someone somewhere in the world will pump out terabytes of junk just to ruin the system for

If its easy and annoying then there does not need to be a motivation. Someone somewhere in the world will pump out terabytes of junk just to ruin the system for others. And banning spam IPs is a kind of crap solution. Spammers would be running on home network IP spaces mostly so as those addresses shuffle around you end up banning most legitimate users as well. I have found my self banned from many sites I am only visiting for the first time due to someone else who was on my IP address before.