To envision the future of chatbots/virtual assistants, we need to take a quick trip down memory lane. Remember Clippy? Love him or hate him, he’s ingrained in our memory as the little assistant who couldn’t (sorry, Clippy.).  But someday, this paper clip could be the chosen one. Imagine with me if you will a support agent speaking with a customer over the phone, or even chat support. Clippy could be listening in, reviewing the questions the customer is posing, and proactively providing relevant content to the support agent. Instead of digging around from system to system, good ‘ole Clippy would have their back, saving them the trouble of hunting down relevant information needed for the task at hand.
WeChat combines a chat-based interface with vast library of add-on features such as a mobile wallet, chat-based transactions, and chat-based media and interactive widgets, and exposes it all to businesses through a powerful API that enables businesses from mom and pop noodle shops to powerhouses such as Nike and Burberry to “friend” their customers and market to them in never before imaginable ways. Over 10MM businesses in China have WeChat accounts, and it is becoming increasingly popular for small businesses to only have a WeChat account, forgoing developing their own website or mobile app completely. US technology firms, in particular Facebook, are taking note.
Chatbots succeed when a clear understanding of user intent drives development of both the chatbot logic and the end-user interaction. As part of your scoping process, define the intentions of potential users. What goals will they express in their input? For example, will users want to buy an airline ticket, figure out whether a medical procedure is covered by their insurance plan or determine whether they need to bring their computer in for repair? 
This is great for the consumer because they don't need to leave the environment of Facebook to get access to the content they want, and it's hugely beneficial to Politico, as they're able to push on-demand content through to an increasingly engaged audience - oh, and they can also learn a bunch of interesting things about their audience in the process (I'll get to this shortly).
As with many 'organic' channels, the relative reach of your audience tends to decline over time due to a variety of factors. In email's case, it can be the over-exposure to marketing emails and moves from email providers to filter out promotional content; with other channels it can be the platform itself. Back in 2014 I wrote about how "Facebook's Likes Don't Matter Anymore" in relation to the declining organic reach of Facebook pages. Last year alone the organic reach of publishers on Facebook fell by a further 52%.
Natural Language Processing (NLP) is the technological process in which computers derive meaning from natural human inputs. NLP-Based Conversational Bots are machine learning bots that exploit the power of artificial intelligence, which gives them a “learning brain.” These types of conversational bots have the ability to understand natural language, and do not require specific instructions to respond to questions as observed in types of chatbots such as Scripted and Structured Conversational Bots.
Before you even write a single line of code, it's important to write a functional specification so the development team has a clear idea of what the bot is expected to do. The specification should include a reasonably comprehensive list of user inputs and expected bot responses in various knowledge domains. This living document will be an invaluable guide for developing and testing your bot.

ELIZA's key method of operation (copied by chatbot designers ever since) involves the recognition of clue words or phrases in the input, and the output of corresponding pre-prepared or pre-programmed responses that can move the conversation forward in an apparently meaningful way (e.g. by responding to any input that contains the word 'MOTHER' with 'TELL ME MORE ABOUT YOUR FAMILY').[9] Thus an illusion of understanding is generated, even though the processing involved has been merely superficial. ELIZA showed that such an illusion is surprisingly easy to generate, because human judges are so ready to give the benefit of the doubt when conversational responses are capable of being interpreted as "intelligent".