I've implemented Facebook Messenger bots for most of my B2C clients for lead generation purposes, using Chatfuel.
I always create dedicated Facebook advertising campaigns connected to these bots, experimenting with different entry points leading to dedicated flows.
For instance: a quiz, a calculator, a test of some sort, gated access to premium content, etc. The bot is the destination where I lead the users. There I use a subtle mix of smart automation and live engagement to try to convert them. And, trust me, it works pretty well. I've generated thousands of leads using Facebook Messenger bots.
If there was just one reason why you should have a Facebook Messenger bot, it would be the obvious following one: each bot activation opens a conversation. Each inbound click you get into the bot opens a thread with a potential customer. Compare this with the usual anonymous visit to your website, the one you would pay £0.1 to £5 or more depending on your industry. If the web visitor doesn't buy anything, sign up, register for a newsletter or leave their details one way or another, the only chance you have to get their attention back is to use display retargeting (which means throwing some extra money on the table). It's better than nothing but not as powerful as the opportunity to convert them on the fly in a conversational format.
Compared to traditional forms (even the most advances ones, like Typeform), Messenger conversations can be monitored all along the way. You can see the conversation unfolding in real time. So you can easily identify drop out points (where the chat stops), improve the copy of a question or even re-engage with the users, both through automated / timed triggers and live prompts (e.g. "if user X didn't answer after N minutes" (= if a specific variable attached to a chat step is "not set"), send them a message to ask them again, kindly, in a slightly different way).
There's just one little issue at the moment with Facebook Messenger UX for Facebook Pages. All messages land in the inbox, even the automated exchanges. It would be great if Facebook enabled us to set rules archiving specific messages, it would remove the hassle of marking as "done" all the fully automated conversations.
Wanna launch a Facebook Messenger bot for your business? Contact me, I'll be happy to help.