Chris:
Please feel free to elaborate on your assertion that RTG's wouldn't have the issues that solar panels do. How would the vehicles be fueled without such solar panels? And as a sidenote, do you think hydrogen-related fuel cell technology could make it in Mars' cold climate? Unfortunately antifreeze isn't particularly light... Solar panels seem to have considerable appeal but if NASA simply offered competitive prizes regarding Mars (http://www.spaceprojects.com/prizes ) then many more players could try innovative approaches and we'd see which ones work the best.

Meanwhile, I wouldn't be surprised if some of the $800 million spent on the twin rovers could have gone to implementing at least one of numerous options for dealing with the dust on the solar panels. It's not like the concepts are foreign to NASA, as a fellow poster here impressively shared with us:

http://powerweb.grc.nasa.gov/pvsee/publications/wcpec2/dart.html

Personally I like Marcia's approach of tilting the panels occasionally and letting mother nature do the cleaning for us. Mars is windy. Meanwhile, if a panel somehow gets stuck in the wrong angle during cleaning, at least it's not blocked off like it could be with a misbehaving (or static-generating) brush. It also wouldn't be blurred like it could be with saran wrap protective coating (whose mechanisms could similarly get stuck or generate static). The gas blower concept that was mentioned seems potentially intriguing too, but it might perhaps add more to mass than the tilting options would.

When money runs out on Earth for operating the rovers, solar panel preservation measures could make it possible for private industry to bid on rights to continue with rover operation. Admittedly, though, JPL is almost as protective of its niche as NASA is. Commercialization terrifies many of those folks. Meanwhile, though, we're still not a multiplanetary species even as bin Laden remains free to wreak havoc.