On the other part if they deliver, they will have a new medium that is amenable to advertising and is fit for mobile use, unlike the text search box. That means they have to be able to answer in human language to any query and remember the whole conversation context.
Right now I am trying hard to learn how to command Google Now to do useful things. It's hard and I discover new tricks every day. I think it is extremely limited at the moment, and poorly integrated in the system. I want to control the apps, to add my own words/phrases/scripts/external apis to it, I want it to fake a believable casual conversation and to have a little more personality.
At some point in the future audio recognition will be good enough (if it isn't already) and understanding of meaning will have become useful enough to make it easier than any other way of interfacing to a computer when giving various commands or searching. Then everyone will adopt it en masse.
Lose what to Facebook? I suppose there's a "chatbot" war now but so-far Facebook's chatbots have opened to terrible reviews. The chatbot market has a long way to go and I suspect it's one place where best will quickly outpace first if things do get going.
Google controlled the search engine market before they AI-ified their search engine and find myself usually using it the same way though occasionally jumping to full questions - which it does OK at. So here it's hard to tell whether AI actually help Google compete.
The rise of text-messaging shows that text is often the superior medium even for people who fully understand natural language. I'd rather send or receive text than deal with voice mail - phone calls for people I care about or things that are hard to understand.
I hope Google doesn't end up in the same boat Microsoft is in with Cortana.
It's a bit buried though; you have to go to System Preferences -> Dictation & Speech and turn on Use Enhanced Dictation, then go to System Preferences -> Accessibility -> Dictation and Enable the dictation keyword phrase.
By default it's "Computer" but it can be "Hey Siri" or anything you want, so you can say things like "Computer, switch to Safari" and "scroll to the bottom" etc.
I wonder why Apple hasn't advertised this more prominently. It seems to be an edge over whatever's available in Windows.