Not to be persnickety, but I believe Plume is the term you guys are looking for. That is when the natural sugars in tobacco begin to crystalize on the surface. Bloom is a term more often associated with molds and bacteria. Though bloom may be the correct term. Only way to truely tell is to get the flake under a high magnification. This is something most folks simply aren't equiped to do, at least not at home.
Under magnification, Plume will have an unmistakable crystaline structure. Molds (at least the more common varieties found in most homes) will have a shape reminiscent of a mushroom.
That said, I have a bunch of SJF myself ranging between one and two years old that exibits this exact same characterist and, as beezer pointed out, it's just awesome stuff. I think having their flakes plume up, even after just a couple of years, is pretty common for SG products. Another reason I find them to be a top of the line blender.
