I have only stayed in an Airbnb three times as a guest, including one trip that was booked by someone else so I had no direct contact with he host. I haven't stayed in touch with the other two hosts. One I never met and with the other, it was actually a traditional B&B that was listed on Airbnb, so I wouldn't say I formed a relationship with any of the hosts.
Guests, on the other hand, are another matter, especially as I host in my own home and have had many long-term guests. So, yes, I have stayed in touch with a lot of them.
This month alone, I had New Year's wishes from some and I have two former guests who have become friends visiting me (one just to catch up and the other to stay with me for a few weeks). I will also be seeing a couple of guests that checked out in December. Another two guests who checked out in December wanted to come and stay again from February, but sadly the rooms were already booked. I am sure we will stay in touch though and I hope to host them in the future.
I don't know how many former guests I'm still in touch with, but it's a lot! There are others that I haven't been in touch with for a while, so this is a timely reminder to drop them a note 🙂