Looking at the data on its own it is probably misleading.
While the ratio of smart phone pics rose, and of course P&S dropped it is probably important to look at the total pictures taken by all.
Did the number of DSLR pictures rise or fall?
What I suspect, and it may or may not be true, the number of non DSLR posters probably rose. One reason is that not only did the P&S shooters drop their P&S in favor of the iPhone, there are many people who never carried a P&S that now have an iPhone that will take P&S type quality pics. While most wouldn't necessarily take up posting pictures, however the technology is in their hands and easy to access.
Another thing to consider is how easy it is to upload from your iPhone, compared to most DSLR's and P&S.