My own grandmother, an immigrant from Eastern Europe, was a wet nurse of sorts. Back in the old country, one of her neighbors didn't produce any milk when she had her first child, so my grandmother would express her milk into glass jars and give it to the woman. If she hadn't done that, that baby would've died. There was no formula to be had, and even if it had been available, no one would have been able to afford it. (It's interesting to note that by the time my grandmother arrived in America and had my mom, she opted for formula--even though they were still poor).
So no, this is nothing new, but is it seriously falling back into favor? Do you know anyone who does this? My gut-reaction to the piece was "gross." I can't imagine under what circumstances I would want another woman to nurse my son. Even if, heaven forbid, something happened to me, I don't think I'd want my baby nursing with someone else (although, interestingly enough, I wouldn't hesitate to nurse a baby who was hungry if there was no other food source available).