Well that is the point isn't it?

Clearly this would need to be flushed out and tested and instaban is simply rhetoric.    I'm not going to engineer the entire test here in a forum post,  but that's the top level pseudo code.  However any miner that fails the test should be considered suspect and perhaps subject to an additional test.   A miner with a 1% error rate would have a 1 in 1,000 chance of artificially failing 2 known good blocks.  Make it 3 tests and the odds raise to 1 in 100,000

All this aside.  It seems that pools now need a way to prove themselves reliable.   As much as I like BTCGuild, I have moved away because it is crystal clear that it is now tainted in some way that costs me money.