Something similar happened to an app I built. The direct competitor in the web world (they had no app of their own) posted a 1-star review using his real name no less, mere hours after launch. This was followed shortly afterwards by 2 more with very similar wording. No luck in getting them removed and we just had to live with it, though it no doubt hurt a little that our first 3 reviews were all 'This is app is crap lol'.