[Greenblaster]

VAC is like anti-virus software. Both viruses and hacks/cheats evolve and change, so as to evade detection. The software meant to eliminate these unwanted programs will not be able to stop every one of them, as the users of the programs are often one step ahead. (thanks to everyone that answered with that in my thread regarding that topic a while back)

And the hackers DO get banned, on the server they are caught cheating on, as well as every other SpawnPoint server. Server admins and honest players like yourself take demos of hackers for that exact reason. If the Anti-Cheat Team believes the demoed player is actually hacking, then the player's Steam ID will be permanently banned from every single SpawnPoint server.