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Google Inc.’s (NASDAQ: GOOG) YouTube may be Netflix Inc.’s (NASDAQ: NFLX) biggest problem. Despite deals with content companies that now includes Sony Corp.’s (NYSE: SNE) TV operation, possible deals to form partnerships with cable companies and the success of its new original content, led by widely regarded “House of Cards,” YouTube’s size and Google’s balance sheet could quickly create a premium video rental and purchase giant. And YouTube began to build such an operation two years ago, an operation that it barely promotes. That could change quickly.

The management at Google cannot fail to see the progress and profitability of Netflix, Apple Inc.’s (NASDAQ: AAPL) TV and Amazon.com Inc.’s (NASDAQ: AMZN) premium video business. Netflix has more than 38 million subscribers around the world. Its revenue run rate is above $4 billion, and operating income is $200 million by the same measurement. While the figures are not especially large by Google standards (its revenue was $14 billion last quarter), premium video sales are one way for Google to show it is something more than a search advertising company.

While YouTube’s premium video service does not have the movie inventory Netflix has, the service does have many recently released films. Google has the financial capacity to build out the YouTube library if it wants to. Studios likely would be receptive. YouTube would give them one more conduit to improve revenue that has been harmed by the death of the DVD and flat theater ticket sales numbers.

YouTube’s largest advantage is simply its size. In August, according to comScore, Google sites, dominated by YouTube, had 167 million unique visitors. That dwarfs the next company on the list — AOL at 71 million. Videos watched on YouTube topped 17.4 billion. YouTube has a larger market, by far, than any other property in the United States, either paid or free. And the Google property has a similarly dominant position in many other large countries.

Google has proven one thing in its business history. Once it creates a business, or buys one, it may leave that business dormant for some time. Then, the search company either kills it or expands it with substantial resources. Expanded paid content available at YouTube is too large an opportunity for Google to miss.