The Financial Post reports in its Friday edition that they say imitation is the sincerest form of flattery, but what happens when it veers into outright theft? A Financial Times dispatch to the Post reports that rivals contend that Costco's recent forays into look-alike clothing have taken emulation a step too far. Last week Lululemon sued Costco in federal court in California, alleging that it had illegally copied at least six patented clothing designs, including its popular Scuba hoodie and Define jacket. Big box stores and fast fashion chains have a long history of offering clothing and shoes that emulate the vibe of more exclusive stores. The dupes craze, however, has taken the copying -- and the profits -- to a new level. Costco's latest efforts were more than Lululemon was willing to bear. Costco's $20 sweatshirt mimics the ornamental stitching and pouch pockets of Lululemon's Scuba offering, which sells for six times the price. Lululemon contends in its lawsuit that those specific details violate the "trade dress" patents that it has registered over the past two years. Costco could be on the hook for gigantic monetary damages, while if Lululemon were to lose, it would be open season for other duplicates.