Counting the amount of title tags of a sub-reddit. Whipped together to see which ones on /r/r4r get the most comments.

tag_count.rb

require 'httpclient'
require 'json'

url    = 'http://www.reddit.com/r/r4r.json'
after  = nil
posts  = []
client = HTTPClient.new
tags   = {
  '[M4F]' => 0,
  '[M4M]' => 0,
  '[F4F]' => 0,
  '[F4M]' => 0,
  '[R4R]' => 0,
  '[R4F]' => 0,
  '[R4M]' => 0
}

50.times do |n|
  puts "Requesting page #{n + 1} with after=#{after.inspect}"

  response = JSON(client.get(url, :query => {:after => after}).body)
  after    = response['data']['after']

  posts |= response['data']['children'].map { |child| child['data'] }

  # Stop when there are no more pages left to process.
  break unless after
end

# Count the total amount of comments per tag found in the title.
posts.each do |post|
  tags.each do |tag, _|
    if post['title'] =~ /#{Regexp.escape(tag)}/
      tags[tag] += post['num_comments']
    end
  end
end

# Sort the results in descending order based on the amount of comments.
tags.sort { |left, right| right[1] <=> left[1] }.each do |(tag, amount)|
  puts "#{tag}: #{amount}"
end