2 questions :
1- If 2 people are using your product, and one of them sends a twitter message to the other, is there an infinite loop because they automatically answer each other's messages?
2- The problem I see is how the engine parse the tweets. Is the user expected to hard-code messages, or is there a natural language processing algorithm that parses the messages in a smart way? It's extremly hard to think about each and every line someone might say - that's the main reason why expert systems fails in most cases. Examples like "hi" are extremly easy to program, and are not really usefull. It might help some people that got too many comments / tweets... but then again, some Twitter client that filter the messages received can do that to, and they can have SPAM filters too.