1. An interactive system utilizing short text messages transmitted by Short Message Service (SMS), the interactive system comprising: (a) a plurality of separate advertisements each advertising by non-SMS means an identical product or service and each inviting a response via SMS to a predetermined number common to all of the advertisements, each advertisement requesting the response to the advertisement by texting to the predetermined number a different predetermined SMS short text message having distinct content that identifies the predetermined SMS short text message as being the response to one of the advertisements and not the other advertisements; and (b) a computer system for receiving a short text message sent via SMS to the predetermined phone number in response to the plurality of advertisements, the computer system being adapted to identify the received short text message as being in response to a particular one of the advertisements by searching a content of the received short text message and identifying at least a portion of the distinct content associated with at least one of the advertisements in the content of the received short text message, the computer system being operable to send an automated short text message via SMS in response to receiving the received short text message.