The recent upswing in firearms purchases is likely fueled by two things. The first and most obvious is the underlying concern of a majority of Americans that the federal government is likely to implement more restrictions on firearms and they'd like to get one before they cannot...hence the increased sales of semi-auto rifles. This buying spree in the face of a potential ban also implies they have no intention of complying with any confiscation efforts either.
The second is a little less obvious, but I believe that Americans are paying attention to the current economic crisis in Europe and the looming one here and understand that increasing economic disruption leads to rising crime:
For this reason we are acquiring handguns for personal and home defense. If this is true, then it speaks well for a significant portion of the population; aware and realizing what may be coming down the pike.
This article sums it all up: