Picture this: Top short seller makes an extreme bet

The enthusiasm in GoPro stock is unwarranted and deserves to be shorted, Dialectic Capital's John Fichthorn said Wednesday.

"It's a company that is trading at a high multiple for what it is, which is something that we often look for," he said. "GoPro pitches itself as a ... almost a media company, which has helped it garner this amazing multiple relative to the fact that it is just a consumer electronics camera company.

"It's funny, on their website they say they're a versatile camera company, but you can't find the word 'camera' in their SEC filings."

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On CNBC's "Halftime Report," Fichthrorn, who is short GoPro stock, said that the "adrenaline-junkie camera market" is a small one. GoPro cameras have gained a following among extreme sports aficionados,

"It's 10 million devices, and they already have 80 percent share," he said. "You know, Apple invented the tablet, and it's gone from 100 percent share to 30. GoPro is not going to be able to hold on to this incredibly high percentage that it's got today."

Fichthorn said that the camera-maker's product line is already competing with "things like your basic smartphone that already has [high-definition 1080 pixel camera], that you can stick in a plastic case and get wide-angle viewing and attach it to a stick, and it's basically a GoPro."

He said that it was a question of whether GoPro was going to lose market share to other companies.

"It's a hypercompetitive, low-margin business in the camera business, as opposed to the media business," Fichthorn said.

By CNBC's Bruno J. Navarro. Follow him on Twitter @Bruno_J_Navarro.