I have occasionally used few sites with chatbot function: a small window appears in the bottom of the page with some smiling avatar there and "message" like "Hi! I am willing to help you! What's your problem?" Then, whatever I write here, the reply is: "Please enter your phone number and e-mail so that we can contact you!" Could have told that in the beginning! Russian reality is warped.
Is is more complex to check the data entered into chatbot and probably it is much harder to fix errors if I find any. GUI is established with many kinds of elements like buttons, lists, back/forward navigation and others, chatbots will need to emulate all of that with text.
If you use Slack (http://www.slack.com) it's quite useful to be able to talk to chatbots and pull out information in chat.
I was using it when I was programming for a startup. It makes things quite interesting, but it's more like a Q&A information retrieval...
