He has shown strength with his arm
and has scattered the proud in their conceit,
Casting down the mighty from their thrones
and lifting up the lowly.
He has filled the hungry with good things
and sent the rich away empty.
It's clear from this, and from other parts of Luke's text, that Jesus may well have inspired Robin Hood to rob from the rich and give to the poor. Mary's song doesn't pull any punches here, showing that the proud, mighty or rich will be brought low suddenly and powerfully, for the sake of the lowly and hungry. Jesus' arrival in the world isn't all fun and games. It's a redistribution of the wealth so that the hungry are fed by the rich, and to do this the rich must give up their conceit, their thrones and their wealth.
When I read things like this, I find it hard to reconcile the contemporary practice of giving useless or frivolous gifts to each other with the arrival of Christ in the world. To celebrate Christmas as a Christian would surely mean giving gifts to the hungry and lifting up the lowly, and not giving half-arsed gifts to other family members who are already overflowing with trinkets.