Because there are so many "hosts" in big cities, it may be a good idea to list them by the most recent log-in.
Many users haven't logged in for 6-12 months and the cities are just a jumble of hosts, making it near impossible to get a response. I don't like the technique of sending 10 responses in hopes of getting a single reply.
Instead of sending people a reminder once a year to log in, it may be better to do the same but delete the account if it doesn't get activated within 4 weeks of the email.
I dare say 20% of the people would disappear.