What would you find unethical? Surely there's a line somewhere.

If an "extreme no poach" agreement does, however, limit my future choices, then such information should be disclosed to me prior to employment. Even this more extreme form isn't inherently deceitful if disclosed. If not disclosed, then it would be unethical.

Note that California (and likely US Federal) law makes no poach agreements of any form illegal, thus making disclosure quite tricky. Of course, their illegality also makes it much easier for partner firms to cheat.

Thus, under the circumstances, the "soft no poach" agreement would be ethical: It requires no employee disclosure to remain ethical. The "extreme no poach" agreement, however, can not be rendered ethical in the current legal environment.

In reality, the no-poach agreements Jobs and others held expressly forbid firms from hiring the other's employees even if the position was sought solely by the employee herself.