NEW YORK - Facebook's Instagram Stories, a clear Snapchat clone, now has more daily users than Snapchat itself. It's something parent company Snap Inc. should be very worried about.

Snap's stock has fallen 45 per cent since its initial public offering in May. While the doom doesn't spell imminent death, it's a sign that Snapchat could be relegated to the sidelines as a niche app -- or worse, a passing fad -- rather than a major competitor for digital ad dollars.

Snap CEO Evan Spiegel has long defended the company's decision not to make user growth its primary mission. But investors care. Facebook, with its 2 billion users, is enjoying record-high stock prices. Twitter, with its growth barely budging, is not.

Snap is scheduled to disclose second-quarter results after the market closes on Thursday.