Yahoo no longer has a QA/testing team - the engineers are expected to test their own code by writing automated quality checks.

“‘It was not without pain,’ Maimon says—though the problems were not as big as he feared. ‘We expected that things would break, and we would have to fix them. But the error that had been introduced by humans in the loop was larger than what was exposed by the new system.’

’It turns out,’ Rossiter chimed in, ‘that when you have humans everywhere, checking this, checking that, they add so much human error into the chain that, when you take them out, even if you fail sometimes, overall you are doing better.’”

Reading the rest of the article it sounds like the move was done in quite an engineering-hostile way, but that aside, 'fewer people involved = fewer errors' is probably a good rule of thumb for building anything.