I got this from Snopes.com from a list of New Rules for 2006. They apparently debunked the claim that is was from George Carlin and instead show (or claim to show) that is from Bill Maher's HBO show.
New Rule: The more complicated the Starbucks order, the bigger the asshole. If you walk into a Starbucks and order a "decaf grande half-soy, half-low fat, iced vanilla, double-shot, gingerbread cappuccino, extra dry, light ice, with one Sweet-n'-Low and one NutraSweet," ooh, you're a huge asshole.
Whatever the source, I think it contains a lot of truth because when people get this picky, it is sign to me that they are oblivious -- or worse yet take great glee -- at acting like petty tyrants, at imposing difficulty and complexity on someone with less power, at showing everyone in the store how skilled they are at pushing around the poor clerk, and at slowing the flow of the line.
Of course, bad cell phone behavior is worse. I was in a long line at a small Post Office in Menlo Park (October 16th was the final day to pay 2005 taxes in the U.S., so the line was long), and was amazed by a woman who spent a full 30 minutes shouting into her cell phone about her experiences on jury duty. OK, I understand a short quiet conversation, but she was talking very loudly and didn't seem to notice the TWO large signs that asked customers not to talk on their cell phones. I suspect that there is an entire book to be written on "Cell Phone Tips for the Complete Asshole."