My thought is, even if you say "please don't" that doesn't mean the person you are speaking to will act accordingly. However, regardless of what media outlet is available, people still have to remember the maxim, don't believe everything you hear/read. Just because someone tweets about how you told them you think a certain manager is lazy, it's hearsay, so I don't see how it is at all possible that you could lose your job over it. I would think the tweeter would be more at risk. In this hypothetical scenario, I would simply deny ever having said anything of the sort to that person, putting that person on the spot, not me. So my advice to anyone potentially divulging something someone told you, unless you have proof, you're the one at risk of losing your reputation/job.