The only defense you have is to nit pick. Nit pick away, I ‘m not impressed. Nor are millions HIGHLY satisfied iPhone users.
Right now it's early in the product cycle. iPhone4's are in short supply and somebody that's got one they don't want can easily find a buyer. Later in the product cycle the market will be saturated and the return rates will be higher because people get them as gifts or prizes and already have one, or are waiting for the next release. If the 6% return rate was over the entire lifecycle of the 3GS, then it's possible you were impressed with a cheap marketing gimmick based on a little statistical apples-and-oranges comparison.