Interesting. The idea that null results are not worth publishing has since the very beginning struck me as one of the most fundamentally flawed ideas in science. Interestingly, it seems to be very domain-dependent. In my field (astrophysics), null results are fairly frequently published, but I've heard that in other fields it's totally impossible to do.
I've run across one or two compiler optimization papers where the conclusion given was that the proposed technique didn't work out so well, but on the whole, it seems it applies there as well. I agree that it's a problem -- if a null result is not published, other people will probably waste years making the same mistakes.
Yeah, the wasted repeated effort was what I initially thought about, too. The argument about how compilations of results will be systematically skewed by certain results not being published is perhaps even more persuasive, because it doesn't just lead to wasted effort but to incorrect results.
