The jumper colon Jul 14 2010
Over at The Millions, Conor Dillon notes the increase in use of colon in contemporary journalism, including a new kind of colon called the jumper colon, "the Usain Bolt of literature".
For grammarians, it's a dependent clause + colon + just about anything, incorporating any and all elements of the other four colons, yet differing crucially in that its pre-colon segment is always a dependent clause.
For everyone else: its usefulness lies in that it lifts you up and into a sentence you never thought you'd be reading by giving you a compact little nugget of information prior to the colon and leaving you on the hook for whatever comes thereafter, often rambling on until the reader has exhausted his/her theoretical lung capacity and can continue to read no longer.
Bottom line: the 140 character limit of Twitter and general move towards concision in online writing is credited for the rise of the jumper colon.