They're definitely legit. When they first started they weren't really "with it" yet and they offered free shipping on all pet food and had all kinds of awesome coupon codes too. I used to get all my kibble from them.. then they got smart and started limiting the codes.. now they don't ship pet food free. Guess that's what happens when a company gets popular!
My guess, and I could be totally wrong, is that maybe Petcurean is changing their packaging and wants to get rid of all of the old bags. Only reason I say that is because the one time I've gotten food so cheap it was Merricks Before Grain and it was right when they were changing to new packaging. My local pet store had all the old bags half off, it was awesome!