Malicious chatbots are frequently used to fill chat rooms with spam and advertisements, by mimicking human behavior and conversations or to entice people into revealing personal information, such as bank account numbers. They are commonly found on Yahoo! Messenger, Windows Live Messenger, AOL Instant Messenger and other instant messaging protocols. There has also been a published report of a chatbot used in a fake personal ad on a dating service's website.
Since 2016 when Facebook allows businesses to deliver automated customer support, e-commerce guidance, content and interactive experiences through chatbots, a large variety of chatbots for Facebook Messenger platform were developed. In 2016, Russia-based Tochka Bank launched the world's first Facebook bot for a range of financial services, in particularly including a possibility of making payments.  In July 2016, Barclays Africa also launched a Facebook chatbot, making it the first bank to do so in Africa. 
Although NBC Politics Bot was a little rudimentary in terms of its interactions, this particular application of chatbot technology could well become a lot more popular in the coming years – particularly as audiences struggle to keep up with the enormous volume of news content being published every day. The bot also helped NBC determine what content most resonated with users, which the network will use to further tailor and refine its content to users in the future.
According to the Journal of Medical Internet Research, "Chatbots are [...] increasingly used in particular for mental health applications, prevention and behavior change applications (such as smoking cessation or physical activity interventions).". They have been shown to serve as a cost-effective and accessible therapeutic agents for indications such as depression and anxiety. A conversational agent called Woebot has been shown to significantly reduce depression in young adults.
In other words, bots solve the thing we loathed about apps in the first place. You don't have to download something you'll never use again. It's been said most people stick to five apps. Those holy grail spots? They're increasingly being claimed by messaging apps. Today, messaging apps have over 5 billion monthly active users, and for the first time, people are using them more than social networks.
This is where most applications of NLP struggle, and not just chatbots. Any system or application that relies upon a machine’s ability to parse human speech is likely to struggle with the complexities inherent in elements of speech such as metaphors and similes. Despite these considerable limitations, chatbots are becoming increasingly sophisticated, responsive, and more “natural.”
Of course, each messaging app has its own fine print for bots. For example, on Messenger a brand can send a message only if the user prompted the conversation, and if the user doesn't find value and opt to receive future notifications within those first 24 hours, there's no future communication. But to be honest, that's not enough to eradicate the threat of bad bots.
If the success of WeChat in China is any sign, these utility bots are the future. Without ever leaving the messaging app, users can hail a taxi, video chat a friend, order food at a restaurant, and book their next vacation. In fact, WeChat has become so ingrained in society that a business would be considered obsolete without an integration. People who divide their time between China and the West complain that leaving this world behind is akin to stepping back in time.