This is more into AI than Ads. AFAIK Siri uses Wolfram Alpha for its answers. Given the way Google's knowledge graph is advancing, it totally makes sense for them to build their own AI engine.
Shutting down Freebase was a big hit for many projects in the AI space, Freebase had 2,903,361,537 facts in comparision Wikimedia's Wikidata has just 13,924,224 facts - that's still a huge difference.
http://en.wikipedia.org/wiki/Freebase , http://en.wikipedia.org/wiki/Knowledge_Graph , http://en.wikipedia.org/wiki/Blekko , http://en.wikipedia.org/wiki/Powerset_(company) , http://en.wikipedia.org/wiki/Knowledge_Vault , http://venturebeat.com/2015/03/27/ibm-acquires-web-crawling-...