It seems extremely petty to me, along with being unbiblical and--from a Christian perspective--unethical.  What does Mars Hill Seattle hope to accomplish?  Are they gonna stand around high-fiving each other?  Is Mark gonna get a big pat on the back and a "job well done" by his staff?  They can't trademark the name Mars Hill because it's in the Bible.  Anyone can use the term if they want to.  It's as silly as (reportedly) Paris Hilton wanting to copyright the term, "That's hot."  If Mark truly wants his church to be effective in society "that's not" the way to go about it.