We've been victim of this as well, but there isn't a whole lot to be done about it, unless you want the BLM to step in with more reg's/fees/permits/etc. It's really no different than other 1st come/1st serve campgrounds. If it's taken, either bribe with beer to share the site, or move along. To avoid this, I try to go midweek, or get up there butt-crack early on fridays.
4 out of 3 people have trouble with fractions.