In today's Lying in the Gutters, Rich Johnston ponders about the possible conflict between the UK tv series Spaced, reportedly coming soon in the US to Bravo, and a Platinum Studios tv project/Top Cow comic of the same name. He asks for someone to sort it out, so I'll oblige.
A quick search of the Trademark Electronic Search System (Tess) shows that no one in the US has a registered trademark on "Spaced" (though there are a few for "Spaced Out"). Now while it is not uncommon for comic books not to bother with the time and expense of registering a trademark (and utilize an unregistered mark), I would think that if you're going to the expense of making a television series, you would want the added protection that a registered mark provides.
So, first one to register wins!
(I should note that It is possible, though unlikely, that the USPTO is refusing to accept any trademark on the word.)