It’s been a year to remember for shareholders of Shopify (SHOP.TO). The ecommerce platform provider is among the top performers on the TSX Composite for 2017, rising more than 130 per cent to trail only Kirkland Lake Gold and Canopy Growth.

Much of the investor enthusiasm can be attributed to Shopify’s explosive revenue growth. While the company is not yet consistently profitable, revenue growth consistently exceeded 70 per cent over the course of the year as the company continued to post record user growth.

In spite of the consistent top line growth, even Shopify’s most ardent supporters have no illusions that the company can continue to grow revenue at this pace.

HollisWealth portfolio manager Jason Del Vicario, who holds shares of the company across all three of his Hillside Wealth Management Portfolios, said that while this pace is unsustainable, he’s more focused on how much, and how quickly, it deteriorates.

“Their top line can’t continue to grow at 70 per cent forever, so I think the market would watch for the pace of deceleration,” Del Vicario said in a phone interview. “The longer than the topline growth can be elevated, the more I think it will help the stock price.”

Though the overall customer growth has been strong, there have been concerns raised over the quality of the merchants hopping on board, and calls for clarity over how long they stay.

In a scathing short report posted October 4, Andrew Left of Citron Research unloaded a volley of allegations, including claims the company’s merchant turnover rate, or churn, is extremely high, while simultaneously accusing Shopify of being a multilevel marketing scheme.

None of Left’s allegations have been proven in court.

While Shopify CEO Tobi Lutke was initially mum on the allegations, it took less than a week before he fired back on Twitter, calling Left a “short-selling troll.”

Though Left’s accusations were wide-ranging, his concerns over the lack of disclosure of the churn number have been echoed by some member of the analyst and investment community.

Stephen Takacsy, the President, CEO and Chief Investment Officer of Lester Asset Management, who does not own Shopify, said he doesn’t agree with Left’s allegations, but thinks Lutke would be well-served to assuage the market’s desire for greater clarity.

“I think they just don’t want to say it: I think it’s probably very high, but just because it’s high doesn’t mean it’s a horrible thing,” Takacsy said in a phone interview. “For the average investor, I think the company should come out and say what the churn rate is. Just come out and say it. Wireless guys, they’ll tell you, it’s no holds barred.”

Del Vicario, for his part, is more or less nonplussed by the issue, given some merchants will inevitably fail to get their businesses off the ground whether they’re using Shopify’s platform or not.

“If you look at the restaurant business or the café business, I think it’s fairly well known that in the first year a lot of new entrants will fail,” he said. “I just don’t see how [Shopify’s] customer experience would be any different from other businesses.”

In spite of their disagreements over the merits of owning Shopify, both Del Vicario and Takacsy agree the stock isn’t cheap. By almost any metric, including price to book, Shopify scans as rather expensive compared to its peers, which Takacsy said could lead to a bumpy ride for investors if the company hits a speed bump.

“Whenever you stumble, or slow down, if the markets get the slightest whiff of something amiss, these stocks are very volatile,” he said. “The higher you soar, the harder you fall.”