I'm in the "not dust" camp myself. That looks more like a delaminating polarizing film, and/or diffuser film.
If you have a nice SLR camera around - and you have a circular polarizer filter - look at your screen and rotate it until it's all black. (extinction) If where the "dust" appears is no different from the rest - then it's likely a failing diffuser. If it's brighter then the background - rotate the filter until the background becomes brighter. If the "dust" gets darker - then it's likely a polarizing filter (on your monitor) is failing.
If you have bright background / dark dust - and then dark background / bright dust - then it's dust or smoke / foreign mattern.
But most LCDs are sandwiched together, with gaskets and / or epoxy - because the polarizer / LCD array / diffuser have critical alignments to each other - so to prevent any movements - they're sandwiched together. It's not like there's any appreciable air-gaps between these components. So if you DO have dust, it's likely on the front of your panel - between the glass exterior panel, and your LCD.