If you run a Git server accessible from a web interface, you need to block Facebook's crawlers. Eversince I started mirroring the XLibre repos my server has been getting DDoSed fucking constantly by Facebook. We lost Checkpoint when we migrated this year so it got really bad. I finally had enough of it.
meta-externalagent is the worst offender. Thankfully, it listens to robots.txt unlike some other aggressive bots I've had the displeasure of dealing with.