The wise comments below got me thinking about this, and how it seems, from where I'm sitting, to be largely a Chick Thang. I just don't see men doing this, at least not in the same way.
This knit from the stash thing is just the latest variation on things taken personally for no damn good reason, and I've been trying to come up with a scenario in which any man I know would act this way. I can't.
Men are just as capable of being jealous and bitchy as women - trust me, I've worked up close and personal with them for my entire career, they also gossip way more than we do, but I digress.
Women (some women) respond to perceived challenges to their decisions and perspective in a way men don't. If a man does something that makes another man question his own choices, he may be openly jealous and now the other guy is and always has been a real asshole. He may be secretly jealous and decide he has to have that Harley or flat abs or better job or whatever and compete with him. He may be secure and a grownup, and admire the Harley and get on with his life.
But whatever way he responds, and women have the same patterns as men most of the time, there is one thing I've never seen a man do - take on the public attitude that the Other Person Is Only Doing This To Make Me Feel Bad About Myself. I have seen this so many times, it has become to me an archetypal response of my gender, and damn, it disgusts me. It is the root cause of the Mommy Wars - hell, it broke out on my old blog, and my baby is 23! You're not allowed to say out loud on the internets that you were a happy working mother who raised functional kids, because it Invalidates MY Choice to Stay Home! Oh, the comments you'll get! I had to have been miserable, or someone else can't be happy with her choice.
This Knit From the Stash Snit (Wendy, you monster - the blood of yarn shop owners is on your hands!) is just a variation on "She lost weight just to make me feel fat."
I do agree with Bess, there's a lot of sheeple jumping on the bandwagon, writing "contracts" with so many weasel clauses they either are lawyers or should be. I think the risk of yarn shops going out of business is somewhat exaggerated. The rest of us will use up our stash until we are no longer burdened by it, and life will go on.
And now I must go work out, because you know, I'm only exercising to make you feel lazy! Mwah-ha-hah!