I would think that the human input is improving the OCR algorithms. I assume that every human correction trains the OCR in some way. With enough corrections the OCR should at some point learn to distinguish between the characters it couldn't before.
The weirdest effect of this is that the most dangerous viruses tend to burn out. If one of those ever came along with a really long incubation time for the disease but a much longer time for contagion that might be a problem.
There are horror movies that scare me much less than something like that.