well, I was thinknig more for web graphics and commerce. if you wanted to use the bmw roundel in commerce it'd be required of you to obtain a trademark license.
I didn't mean to imply that writing on your roundel that you paid for is illegal. but if you modified the roundel (ex.) so that it said JYBUTE instead of bmw to sell, then you are violating the Trademark Dilution Act, no questions asked. if you modified the logo in parody you might get away with it.
BMW in particular is very protective of their trademark, and if you in anyway want to use their logo commercially then they are likely to take legal action.
bimmerwerkz was asked by BMW to remove the roundel in their header. and they did and didn't have any problems.