I suspect the mirrors are starting to flake out on the chip. I can't say anything about the longevity of Samsung DLP sets, nor can I say whether they use the same piece as Mitsu's (probably not). But it's akin to a dead pixel on an LCD set. I assume the specs are essentially as small as a pixel?
The dark/white specs are probably where the mirrors are away/towards the light source and stuck there. The flickering perhaps where that particular mirror is flipping out and won't sit still (which they all do anyway), but not where it is supposed to be hence you noticing it.