I question whether or not dust filters would be very effective. Air pressure at the intakes on MacBooks is pretty high since the slits are so small. I'm often classified as a fanboy, but I've taken apart many of my Macs and almost never have they had any more dust than my PCs—including laptops. I think the primary difference is that Apple seldom uses conformal coating on more sensitive areas unlike certain laptop manufacturers. The solution is pretty easy, I'd think. They just haven't done it yet. At the same time, I'd be interested to see what percentage of users this is happening to. It's ought to be pretty minimal.