Nobody at Google is saying. Mozilla doesn't seem to have any problem with Ahoy!: it is still available for Firefox.
So why is Google dead set against Ahoy!? Could it possibly be because Ahoy! is an anti-censorship tool? "Don't Be Evil" Google couldn't possibly be kowtowing to China's censorship, could it? (Of course, the fact that Google won't say anything about reports that it is starting up, or has bought, a censored search app for China don't help tamp down the rumour mill any ...)
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