>*trademarks _must_ be defended, or you lose them* //
I think this is actually a myth - certainly in Europe, not sure about the USA & elsewhere.
Moreover, you can give anyone a license to use your marks without making a charge. The point is not to allow the terms to pass in to general use - to become a verb for example - that's why Google never talk about "googling" as a term for 'using a search engine'.
If it weren't a myth then mega-corps would be forever getting out of trademark infringement proceedings by having created a tiny little "business" somewhere hidden that the mark owner never knew about and saying that the owner therefore wasn't protecting their marks and so should lose them.
In Europe at least you must simply use the registered trademark (and pay your fees) to retain it - 'The ECJ has said that the handing out of free drinks labelled 'Wellness-Drink' was not "genuine use" of the Wellness trade mark in the drinks category. The EU's Directive on trade marks says that trade marks can be revoked after a five year period in which no "genuine use" of it was made.' (http://www.out-law.com/page-9718)
Also this relates well: "It said that the Zappa name had only been used as part of a domain name of a website based in the US but accessible from the EU. That website had not used the trade mark to sell or advertise products for the EU market, though, and so was not used in trade." (http://www.out-law.com/page-11202)
IANAL