In the last 12 months, a rush of investments in digital media companies has pumped up valuations. Disney invested in Vice at a $4 billion valuation, the same value it paid for Star Wars’ maker Lucasfilm in 2012. NBCUniversal invested in BuzzFeed at a $1.5 billion valuation. A handful of other online publishers got valuations in the hundreds of millions.

But with competition for digital ad dollars increasingly tough, many of these companies are diversifying into traditional media businesses like licensing programs to TV networks. That trend makes these valuations appear increasingly beyond rational, in the view of several executives at traditional media firms.