Ever see a worse DIY fail, @joelfisher? I once tried using a glass soda bottle for wallpaper and made a huge wet smear. Some ideas just need to be left in the pantry, because the right tool really does make the job work.
Actually, that wet smear might've happened because wallpaper paste needs to soak in first. A bottle wouldn't let the paper breathe like a real sponge roller does. It's a bummer when a shortcut just makes more work.