One of the questions is: "who sings that song where the guy goes 'How Bizarre'?" Google Glass provides the right answer (OMC) and lists a few sites that mention this answer. I asked a similar question using the mobile Google Search app and Google displayed the following message below the answer: "mentioned in results below".
It's nice to see that Google understands verbose questions. Unfortunately, Google no longer mentions the sources that provide the answer. For example, a query like [everest height] used to return an answer, followed by a list of sources.
Here's how it looks today, after the upgrade to the Knowledge Graph:
Google extracts facts from various web pages, so listing some of the sources is appropriate and helps users find reputable sources of information. If the answer is wrong or it's no longer accurate, Google can always point to the sources. As Wikipedia says, "verifiability means that people reading and editing the encyclopedia can check that the information comes from a reliable source".
Google mentions that the "Knowledge Graph isn't just rooted in public sources such as Freebase, Wikipedia and the CIA World Factbook. It's also augmented at a much larger scale because we're focused on comprehensive breadth and depth. It currently contains more than 500 million objects, as well as more than 3.5 billion facts about and relationships between these different objects. And it's tuned based on what people search for, and what we find out on the web."
Here's an example of wrong answer: Google's answer for [hardware wars running time] is 60 minutes, even though the right answer is 13 minutes.
Another wrong answer: Hardware Wars was actually released in 1978.