Shopify Inc. ( SHOP-T ). Canada's tech sector has a new top dog. A meteoric rise in Shopify Inc. shares in recent weeks has made the Ottawa-based e-commerce giant the single largest IT listing in the country, a title previously held by home-grown champions of technology past and present, including Nortel Networks Corp., BlackBerry Ltd. predecessor Research in Motion Ltd, and, most recently, CGI Group Inc. With a $24.7-billion market capitalization, Shopify finds itself atop Canada's tech sector at a pivotal stage in its evolution. Questions linger from a 2017 short-seller attack over Shopify's business model, competitive threats are rising and profitability is still proving elusive.