quick script takes a file of URLs and tells FB to recrawl them. When og:image etc have changed, this will refresh FB's cache of the page.

fb_recrawl.rb

# pass input file as param
return unless ARGV.size > 0

list = ARGV[0]

File.readlines(list).each do |line|
  puts `curl --data "id=#{line}&scrape=true" https://graph.facebook.com`
end