Having said that, I want to play devil's advocate for a second. It's just my natural reaction when the press embeds big unquestioned assumptions in reporting for the sake of sensationalism -- namely that this is obviously "illegal" and nefarious behavior. Because, after all, it kept down wages for people like me who might otherwise have been more actively recruited.
If your reaction is OF COURSE IT'S ILLEGAL, just hold on a second. Try to think about the counterargument rationally, even if it's against your personal interests. (That's what I'm doing.)
There do exist many precedents for agreements and restrictions on seemingly "competitive" behavior that is deemed "unfair".
Let's consider a related example from another domain: countries "dumping" cheap goods into foreign markets. For example, China is accused of "dumping" subsidized steel into the U.S. market, which hurts the industry here. The U.S. steel industry works with the government to put in place tariffs that block the practice.
So is the U.S. steel industry being anti-competitive here? Have they engaged in an anti-competitive pact with the U.S. government conspiring to keep up the price of steel here?
Well, on the surface, yes they have. But the distinction is that "dumping" is meant to describe a particular form of competition that is short term and unsustainable in nature and designed primarily to destroy competing business. It is meant to isolate a specific practice that actually hurts competition in the long run.
So, what about the practice of poaching employees from competitors? Well think about it for a minute.
What is the value of a Safari engineer to Google's nascent Chrome team? The truth is, it's a lot more than just that engineer's skillset. There's also the value of undercutting Apple's Safari development. That's HUGELY valuable to a competitor.
So, I just wanted to put it out there that at first blush at least, that the practice of "poaching" may actually have an anticompetitive angle. Just like with "dumping", you have to look beyond the immediate act (restricting/boosting prices) and examine the particular practice it's attempting to curtail.