Why don't NASA's $800 million Mars Rovers have solar panel cleaners?
Maybe they can do something like that by manuvering the lander over a small rock or two instead of manuvering the lander around even the smallest rocks.
The Delta-V, "bouncing around" and small amounts of wind resistance generated might cause much of the dust to roll-off the surface. making a cleaning system relatively unneeded.
I do like Tom's Idea though.
Scott