Law 360 reports a motion to disqualify lawyers who interviewed and obtained documents from an adversary's former employees. My sense of this issue has been that lawyers are not sanctioned or disqualified for learning informally information they could obtain through discovery, even if the information would be covered by a former employee's NDA. Lawyers are disqualified if they obtain privileged or work product information.
The Restatement supports that distinction, as I recall, distinguishing confidentiality obligations imposed by law from those imposed by contract. (The motion referenced in this story refers to both proprietary and privileged information, so the distinction may not be relevant in that case.) I have a general, anecdotal sense that companies are becoming more aggressive in attempting to enforce NDAs through disqualification motions or requests for other sanctions. CA has a proposed ethics rule that would support such efforts. It is an interesting issue to watch.