An even better ploy would be a large effort of people publishing e-books of short stories all with the term space marine in the title and the text. IANAL, but

An even better ploy would be a large effort of people publishing e-books of short stories all with the term space marine in the title and the text. IANAL, but I believe the more widely used and genericized a term becomes, the more likely the trademark is to become unenforceable unless Games Workshop is willing to sue everyone who gets involved.