Men actually can lactate, but not through eating afterbirth. There are a couple of ways, none involving technicolor yawns, in which this can happen. The first is if a man takes female hormones. This is an observed and repeatable phenomenon.
The second way was observed among men who had been in POW camps and German concentration camps after WWII. Because they had been starved, their bodies had stopped unnecessary bodily functions, like produce hormones. Because they were no longer producing testosterone, estrogen, progesterone, etc. their livers stopped producing enzymes to break down these hormones. What would happen next is that when they started eating again, they would begin to produce hormones. Lots of them. But their livers still didn't have enzymes to break hormones down and therefore lactating hormones would build up in the body and some of these men would begin to lactate. The third way that men can lactate has already been mentioned by Trina, so I won't repeat it.
It's also worth mentioning that in some species of fruit bats, the males share breast feeding duties. If you're interested in reading more about this, I believe either New Scientist (www.newscientist.com) or Scientific American (www.sciam.com) had a detailed article about this a couple of years back.