As the founder of an open source cloud computing product company my concern with combining open source and trademark law is that although we freely encourage the adoption of our open source software, we still want to control our brand and corporate identify. At the end of the day this is the key piece of the value of an our source company or community. The trademark or brand identity in many cases can be far more valuable then any direct revenue, (MySQL or Apache for example). Like most software -- perception is what matters, Apple is perceived to be more secure, less prone to security exploits, not because it's true but because Apples brand & identity is perceived that way. The same applies to open source.
Giving away free usage to your brand's trademarks would be on par with giving away the keys to the castle.
Just because I'm an advocate of OSS doesn't mean I should give free access to my social security number, my drivers license, and other forms of government identification for everyone to freely and openly use to buy a car, open a bank account, and in other forms use my identity as if it was their own. For those of you who honestly feel that Trademark's are just as menacing to Open Source Software as Copyright's and Patents, please rethink your position. Thanks!