One can think of lots of reasons why this might be the case. A more mature business grows more slowly.
There's less novelty effect. Perhaps it is just the impact of the recession, and more staples are bought at physical locations.
The issue is what happens after the recession ends. There's a line of thinking that with serious deleveraging happening throughout the economy, consumer spending will not return to its pre-recession level.
Off the top of my head, it's hard to see why this line of thinking is wrong, though it is worth noting that consumer behavior often surprises researchers.