It isn't new, and people have been joking about finger smears since this kind of unlock mechanism came out (I remember making this discovery myself and promptly switching my phone back to using a number pad). But it is worse than shoulder-surfing; you can just steal a phone, say, from someone's purse or off a table when no one is looking, and then unlock it. You don't have to stock the person, see them unlock the phone, and then steal it.
I'm OK with shoulder surfing. The main reason I use a pattern lock is that if I forget it somewhere or got it stolen the guy who has it won't know the pattern. Putting that aside, I do was hoping to see an analysis that could help me come out with a pattern that a thief couldn't guess with the traces on the screen.
