Trademarking Open-Source Projects?

dautelle asks: "I had the nasty surprise to receive a letter from a company in New-Zealand asking me to stop using the 'jade' name they have recently trademarked (my open source project has been Java Addition to Default Environment or JADE for short, long before their trademark filing date). I am going to comply, but I wonder if our open-source projects should be trademarked (cost >300$) to prevent such misfortune?"