Quoting Michael Westen:" No. I mean maybe TECHNICALLY I do now but she is 2.5. I let her WIO but no CIO. If she is legitimately crying, she needs something."
Exactly how we see it, too. He's grown out of it at this point since he's almost 4, but at around 2 or so, he would whine, you could tell the difference between the fake, forced cry and if he was truly upset or needing something. If he was fake-crying or whining, we left him there, he eventually just cut it out after a month or so. If he was really crying, then I wouldn't just leave him there.
But not as an infant or baby < 18 months or so. He started the fake cry bit when he was around 18 months.