Twitter's mistake was to ever allow such thing being completely free in the first place.<p>Telco companies will charge fees if an entity (private or public) wants to send alerts over SMS to their customers/users. I can't see why Twitter had to be different other than "we must grow fast!" mentality of a startup hungry for MAU.<p>NYC Subway MTA has significant revenue (>5 bi/year). Sure they can pay Twitter if this is how MTA users want to be notified. Worse case scenario, they will add a $0.01 "Twitter-fee" into ticket prices.