Why it's important to ask this: I am always surprised by how few marketers at any level understand how Google really ranks content. Though you're not interviewing for an SEO position, content marketing is intrinsically tied to search engine optimization; everyone should know the basics when creating content.

What to look for: You don't need a candidate to know the PageRank formula, but rather the basic premise behind Google's ranking algorithm, along with other auxiliary factors that help with SEO. For example, many naive marketers think Google ranks content largely on meta tags and keyword stuffing. In reality, Google primarily ranks content on inbound links, and the authority of the sites doing the linking. It's a bonus if a candidate can mention other contributing factors such as the text of the hyperlink, the title tag, keywords in the URL, and others.