After lots of testing I've concluded that currently Facebook only logs the IP you register from, not the IP you log in from. If you register more than 5 or so accounts from the same IP in a relatively short amount of time, they will get banned. If you register from different IPs and log in from the same IP, you'll be fine.
The only Facebook bots out now are shitty browser-based bots. I tried writing a good Winsock bot for Facebook not too long ago, but got stuck on getting the ReCaptcha and gave up.