You say Google is data driven? Then why not use the available data about a candidate's past?
I work for google, and interview on a regular basis. I am a huge fan of using data of a candidate's past: for open-source projects, I clone the repository and browse through patches, for example. I like this, because real work covers a depth that a 45 minute interview cannot.
Unfortunately, besides open-source work, the only source of data usually is hearsay from the candidate himself, a source which often is somewhat biased.