So which way to hold chopsticks is correct?
Taiwanese often comment on the way I hold my chopsticks (like the top right or bottom left). They are amazed at how proper it looks. This is besides the fact that, even though I've been in Taiwan for almost 10 years, they are still amazed that I can use chopsticks at all.
In fact, most Taiwanese have a very casual way of holding their chopsticks (most like the top left picture but not with the sticks crossed). I think this happens due to them gradually getting more lax holding the chopsticks over time.
Most foreigners, on the other hand, are relative newbies to holding chopsticks. I remember studying the chopstick holding diagram in the Lonely Planet in order to perfect my technique. Thus, we (mostly) have textbook style technique.
I think an interesting parallel happens when comparing holding chopsticks to people holding pens. There supposedly is a 'proper' way and a more relaxed way. I remember teachers trying to correct my relaxed pen holding to no avail. My aunt once said, to the horror of my father, a teacher, that either way gets the job done so either way is ok.
I would agree with her and apply the same thinking to chopsticks holding. One thing the Taiwanese do have to be thankful for is that they were not raised Japanese. The Japanese are infamous for beating out improper chopstick holding from their kids and even forcing lefties to hold with the right. By comparison, the Taiwanese have relative freedom.