GoPro shares fell by more than 8% to start the week.
In an article last weekend, Barron's magazine wrote that the company's stock could fall to $25 a share. That's a 29% decline from Friday's closing price of $35.15.
The stock is already down 44% year-to-date.
Alexander Eule at Barron's wrote that the big downside for GoPro was competition. Eule calls the company's point-of-view cameras a "one-product wonder" and compares them to BlackBerry smartphones that were once all the rage.
The article said Apple was a looming threat; when it emerged in January that Apple had obtained a patent for a camera that could compete with GoPro's cameras, shares fell 12%.
Also, the Chinese manufacturer Xiaomi announced a 16-megapixel camera that was similar to and much cheaper than GoPro cameras.
The threat from other brands is something analysts have been warning about as they have watched the stock price fall.
In early trading on Monday, the stock declined to as low as $33.03 per share.
Shares are down 8% from the time the company went public in June 2014.
