Some of the finest minds in finance seem to have missed the lesson of the nursery rhyme “Humpty Dumpty”: All the king’s horses and all the king’s men couldn’t put that character together again.

They sure are trying. The advocate William A. Ackman has taken a 5.5 percent stake in the $75 billion snack-food giant Mondelez International predicated on the possibility, among others, of putting it back together again with Kraft Foods, which just merged with H.J. Heinz. Re/code, meanwhile, reported that one option for the cloud computing software group VMware could be to absorb its data storage parent EMC.

Both ideas may exist solely in the pitch-books of investment bankers, but the zeal with which investors have embraced them suggests both credulity and excess in the mergers market. After all, shareholders cheered when EMC sold a slice of VMware to the public in 2007, and when the Kraft-Mondelez split was telegraphed four years ago this week.

Times change, but it’s hard to see why winding back the clock would add value in these cases. VMware’s shares have tripled since they went public, giving the company a $37 billion market value. That’s because investors like its profile as an unadulterated software play distinct from the wider-ranging and more mature $52 billion EMC, whose shares have risen by less than half since setting its subsidiary partly free.