Ultimately, only time will tell how effective the likes of Facebook Messenger will become in the long term. As more and more companies look to use chatbots within the platform, the greater the frequency of messages that individual users will receive. This could result in Facebook (and other messaging platforms) placing stricter restrictions on usage, but until then I'd recommend testing as much as possible.
With natural language processing (NLP), a bot can understand what a human is asking. The computer translates the natural language of a question into its own artificial language. It breaks down human inputs into coded units and uses algorithms to determine what is most likely being asked of it. From there, it determines the answer. Then, with natural language generation (NLG), it creates a response. NLG software allows the bot to construct and provide a response in the natural language format.
In 1950, Alan Turing's famous article "Computing Machinery and Intelligence" was published, which proposed what is now called the Turing test as a criterion of intelligence. This criterion depends on the ability of a computer program to impersonate a human in a real-time written conversation with a human judge, sufficiently well that the judge is unable to distinguish reliably—on the basis of the conversational content alone—between the program and a real human. The notoriety of Turing's proposed test stimulated great interest in Joseph Weizenbaum's program ELIZA, published in 1966, which seemed to be able to fool users into believing that they were conversing with a real human. However Weizenbaum himself did not claim that ELIZA was genuinely intelligent, and the introduction to his paper presented it more as a debunking exercise: