I've always considered myself to be a Grammar Nazi. I can understand when people make grammatical errors, but I get really irritated when the error has theoretically gone through some official channels of business. At some point in the creation of this irritating window cling, you'd think that someone would've said, "Hmmm. What's up with that apostrophe? Are the Jones in possession of something? Is the name Jones some sort of contraction that the world is unaware of?"
Maybe everyone needs to see this article: How to Use Apostrophes.