The idea of building a publishing company and media destination built on millions of side doors is the future.

That comes from Erika Nardini, svp of sales and marketing for Demand Media, who was talking to me about one of the quiet, but important, changes happening in the digital media landscape: the diminishing homepage.

Search was first to put a serious dent in the primacy of the homepage. Now, with social and mobile gaining steam, publishers are left without the big, splashy homepage premium ad placements.

The fact is, most publishers see half or more of their traffic come in through the side door, whether through search, social or other means. That means publishers need to create new premium placements in a world where “every page is a home page.”

One of the common ways is the giant Welcome Ad screens you get when you first land on an article. There are other, more opportunistic measures. Last week, Gawker had a hit of a story — it unmasked a notorious Redditor – and chose to plop a video ad interstitial over the story when users hit it from Twitter and Facebook.

Read on.