I learned this one the hard way too, dude. I was following a buddy on an LTZ 400 in the same dusty conditions, and nobody warned us about a 4" log that had fallen and was laying right across the trail. The log was at the beginning of a long straightaway, so we came flying around the corner, totally unaware of any danger. Both of us hit our throttles and began to shift up through the gears. Next thing I know, I see the LTZ and rider go airborne. I slammed on my brakes and skidded through the dust cloud, only to hit the same log and get thrown off. The Blaster flipped, but fortunately didn't hit me. The only casualty ended up being bent handlebars on my bike and plenty of bruises to both of us.
Needless to say, the tree was promptly attacked with a chainsaw and removed. Had the log fallen at the other end of the trail, when we would have been running in 4th gear, things would have been much worse. I learned right quick to never follow another rider too closely when visibility is poor, and to watch EVERYWHERE for hidden hazards. You just never know.