Deutschse Bank downgraded shares of O'Reilly Automotive Inc and lowered its price target, citing three reasons.No. 1: Do-It-Yourself UndosAlthough analyst Mike Baker believes the company will remain the leader in both comps and operating margins, he thinks the incremental competition in the DIY side of the business could limit earnings and revenue beats.The analyst clarified that Amazon.com, Inc. has about 6.2 percent of the $54 billion DIY auto parts after-market industry. If O'Reilly strives to match Amazon's lower prices, the analysts think there could be an issue with gross margins.Read more