I'm not sure if you're saying you're not familiar with the meaning that the word has had since the early 15th century, but http://dictionary.reference.com/browse/poaching?s=t. It's application to business employment is obviously much more recent - I can't find a definitive citation, but I'd be surprised if this usage even dated back to the early 20th century.
I find it an inapt analogy to describe a transaction in a competitive job market.
Since PayPal and Facebook aren't competitors "poaching" isn't an apt description by that definition either. I think "poaching" is just a more dramatic and linkbaity synonym for "hiring".
That's the GGP's point, I think. The word 'poaching' is used because the humans are treated as game, and continuing to use that word continues to bring up that connotation.
I find it an inapt analogy to describe a transaction in a competitive job market.