It appears that Mini USA and Baron Mini have figured out the problems and corrected the issue The Mad Blogger discusses below. Mini is rumored to be doing a full review of how warranty might get cancelled and correcting the problems.
So there are some rumors going around on the internet that Mini USA is voiding warranties of owners who autocross their vehicles. Don't buy a Mini Cooper! Buy a totally different car, from a totally different company because there is a massive chance that Mini USA Sucks! If they are willing to advertise by distributing "cones" in magazines, and then go ahead and cancel warranties of those who race and help promote the brand they should be highly ashamed of themselves. Read more about it on SCCAForums.com
I feel for the original poster, don't shop at Baron or purchase a Mini Cooper anywhere if you want good service!