I wouldn't say those are the reasons the questions suck. The idea of asking it is not to get a good answer but to discover the process by which someone would approach an unsolvable or half-solvable problem. In other words, they use it to see how you think through the problem.

The issue I have is, if you don't know that when you're asked that question, it's easy for a good candidate to freeze up because they don't know what is really being asked of them. In other words, it's like taking someone off the street and giving them the SATs. Their score is going to suck compared to if they prepared for it. So what you're really doing is testing their ability to take an arbitrary test, or jump through hoops. Since Google prefers advanced degrees, they probably are already pretty good at jumping through hoops, so it's a bit of a pointless exercise that can throw off great candidates completely if they aren't prepared for it.