"Unexpected changes in our billing have forced us into a difficult situation with our Canadian SMS service. We can’t afford to support this service given our current arrangement with our providers (where costs have been doubling for the past several months.) As a result, effective today we are no longer delivering outbound SMS over our Canadian shortcode (21212).
The ability to update Twitter over SMS will still be supported over 21212. But we know that this is only part of the experience and we want to make Twitter work in the way folks want … regardless of where they live.
There is a realistic, scalable SMS solution for Canada (and the rest of the world.) We’re working on that and will post more details on the Twitter blog as we make progress."