Need another sign that iTunes will soon be floating your library up to the cloud? Look no further than confirmation of Apple signing Warner Music, a deal that should see the label's music available in its upcoming streaming iTunes service. This is in addition to last week's confirmation that two major labels signed on, though its unclear whether Warner is part of the pair or is, indeed, a third. That might leave only one of the major labels left unsigned -- or maybe Apple's already locked down all four but doesn't want to kiss and tell. Yet.