I always thought of colic as one of those ambiguous 19th century diseases, like consumption or bad humeurs. And even though we went through a few weeks where the kid would go into meltdown for little or no reason, we never considered her to be "colicky."
Whatever you call it, the meltdown-without-cause is apparently still largely a mystery to doctors and researchers, at least according to this NY Times article. There's no medical consensus on what to do: some doctors say it's alright to let a kid cry sometimes, others say swaddling's your best bet. The general principle, though, of trying to calm the kid by recreating the comforting conditions of the womb, is pretty widely accepted, if not rigorously tested.
The whole point of the article seems to be a setup to pitch Dr. Harvey Karp's book and DVD, The Happiest Baby On The Block, which features his "exclusive five-step process" which must be done, in order, to trigger a screaming baby's "calming reflex":
To counter his critics, Karp is very eager to set up a very complex scientific test of his own: "Plans are under way to send one group of parents home with his DVD and another group with a regular child-care video and watch what happens." I'll tell Nature to hold the presses.
[update: this has been the #1 most emailed story on nytimes.com for most of the afternoon/evening. go figure.]