Twitter is no longer delivering outbound SMS over their UK number, due to the high cost from UK mobile operators.
Twitter has worked cost-effective deals in Canada, India, and the United States, so that it can provide full incoming and outgoing SMS service without passing along operator fees in these countries.
Twitter will be introducing several new, local SMS numbers in countries throughout Europe, in the coming weeks and months. These new numbers will make Twittering more accessible for all the folks who have been using SMS to send long-distance updates through our UK number.
The Twitter blog states “Even with a limit of 250 messages received per week, it could cost Twitter about $1,000 per user, per year to send SMS outside of Canada, India, or the US”
Twitter will continue to negotiate with mobile operators in Europe, Asia, China