Twitter is retroactively changing the xAuth rules in a way that will break every existing install of a native client (except the official one), and make every n

Twitter is retroactively changing the xAuth rules in a way that will break every existing install of a native client (except the official one), and make every native client (except the official one) going forward harder to use. Stupidity would be breaking their own clients, too. Stupidity doesn't seem to adequately explain their commitment to going forward with this change, so we turn to Occam's Razor. The simplest apparent explanation for the observed behavior is that they want to discourage the use of third-party clients.