gistfile1.rb

friend_bucket = AWS::S3.new.buckets[ ... ]
follower_bucket = AWS::S3.new.buckets[ ... ]

friend_obj = friend_bucket.objects[ ... ]
follower_obj = follower_bucket.objects[ ... ]

threads = []

threads << Thread.new do 
  friend_obj.write( data, :content_type => ... )
end

threads << Thread.new do
  follower_obj.write( data, :content_type => ... )
end

threads.each { |t| t.join }