1. Yes. All 'power bricks' use a few Watts of electricity merely being plugged in, even if they aren't plugged into their device. So if you leave your power adapter plugged in to the mains power, then even while you are away, it is using a little power.
2. If you are going to leave your computer off, and I mean all the way off, not just asleep, then leave it plugged in for an extra 2 hours after it is fully charged, then unplug it. It will 'trickle charge' for a few hours after it says "full", but even after that, it will still use some power.
If you want to use the least energy possible to recharge your MacBook, then leave your power adapter unplugged until you are ready to plug in your computer, turn your computer off, plug it in, and unplug it from both the computer and the wall as soon as the light turns green. You will only have charged the battery to about 90% full, but the remaining 10% takes more power per % to charge than the first 90%.
Of course, if you're going to these extremes, then make sure to do this for everything in your house that uses a transformer (aka "power brick".) And make sure to unplug any appliances that you aren't actively using, like your TV or VCR. Make sure to keep your freezer as full as you can, as freezers are more efficient when full; but DON'T completely pack your refrigerator, because for some reason, they are LESS efficient when full.) Replace every light bulb in your house with compact fluorescent (or even better, LED,) and turn them off every time you leave the room.
Unless you are trying to be an absolute power-miser (for example, if you live off the power grid, and use solar panels for all your electricity,) there is no reason to go to these extremes. If you have even one standard incandescent lightbulb, it is using more power (than if you had a compact fluorescent,) than leaving your MacBook plugged in even after it is fully charged.
