[pmoriarty]

Adding small amounts of noise is actually sometimes used to improve the performance of various AI techniques. It helps prevent overfitting.

In fact, if your technique or model is seriously affected by a little noise this is usually enough to brand it brittle and maybe even a failure, as it's a sign of overfitting. Anyone working in this field knows to look for this and will try to make what they create more robust.

The design of visual captchas is one obvious indication of just how successful AI techniques have been at image recognition in the presence of noise. It's no longer enough to make them a little noisy. In order to resist being solved by mechanical means, visual captchas have to include so much noise that even humans have problems recognizing them.