From jayski:
Report: NASCAR fines unnamed drivers for comments: NASCAR has fined at least two of its star drivers this season for making critical comments about the racing series, The Associated Press has learned. People familiar with the penalties told the AP the comments were considered disparaging to the sport. The people spoke on condition of anonymity because NASCAR is not publicly identifying the topflight drivers it fined. They say one driver was penalized as much as $50,000. The decision to fine competitors for critical comments puts NASCAR in line with many other professional sports leagues. The NFL and NBA both routinely issue fines for criticism of officiating. It also backs up NASCAR's season-long campaign to rebuild the slumping sport through an improved on-track product and off-track promotion from its drivers.(Associated Press/ESPN.com)(7-26-2010)

From spdracer19:
but unlike the other pro sports they don't have the kahonees to name them so we can know what the comments that hit so close to home were. Or they drive for a high profile team and they are afraid to mention who they are for fear of reprisal from said team owner.