Have you ever seen one of those "warranty void if ..." stickers on your consumer electronics?
Did you know that those stickers generally are worthless because they violate the Magnuson-Moss Warranty Act (15 U.S.C. § 2301 et seq.). The MMWA prohibits tying a consumer product warranty to using another article or service identified by brand, trade or corporate name (15 U.S.C. § 2302(c)). In other words, if you buy an Apple product, Apple cannot say that you have to use Apple repair services otherwise your warranty is void.
Apparently, the Federal Trade Commission (FTC) finally saw one of those stickers. It recently sent out letters to six companies warning them that their versions of that sticker may constitute deceptive practices under the FTC Act (see notice on FTC website).