gistfile1.txt

irb(main):005:0> m = mark.to_h
=> {:fn=>"Mark Wunsch", :title=>["Front End Engineer at Scripps Networks"], :n=>{:family_name=>["Wunsch"], :given_name=>["Mark"]}, :adr=>[{:locality=>["Greater New York City Area"]}]}
irb(main):006:0> m.to_yaml
ArgumentError: wrong number of arguments (1 for 0)
	from /usr/local/lib/ruby/1.8/yaml/rubytypes.rb:41:in `to_yaml'
	from /usr/local/lib/ruby/1.8/yaml/rubytypes.rb:41:in `node_export'
	from /usr/local/lib/ruby/1.8/yaml/rubytypes.rb:41:in `add'
	from /usr/local/lib/ruby/1.8/yaml/rubytypes.rb:41:in `to_yaml'
	from /usr/local/lib/ruby/1.8/yaml/rubytypes.rb:40:in `each'
	from /usr/local/lib/ruby/1.8/yaml/rubytypes.rb:40:in `to_yaml'
	from /usr/local/lib/ruby/1.8/yaml/rubytypes.rb:39:in `map'
	from /usr/local/lib/ruby/1.8/yaml/rubytypes.rb:39:in `to_yaml'
	from /usr/local/lib/ruby/1.8/yaml.rb:391:in `call'
	from /usr/local/lib/ruby/1.8/yaml.rb:391:in `emit'
	from /usr/local/lib/ruby/1.8/yaml.rb:391:in `quick_emit'
	from /usr/local/lib/ruby/1.8/yaml/rubytypes.rb:38:in `to_yaml'
	from (irb):6
irb(main):007:0> {:fn=>"Mark Wunsch", :title=>["Front End Engineer at Scripps Networks"], :n=>{:family_name=>["Wunsch"], :given_name=>["Mark"]}, :adr=>[{:locality=>["Greater New York City Area"]}]}.to_yaml
=> "--- \n:n: \n  :family_name: \n  - Wunsch\n  :given_name: \n  - Mark\n:title: \n- Front End Engineer at Scripps Networks\n:fn: Mark Wunsch\n:adr: \n- :locality: \n  - Greater New York City Area\n"

My output

>> m = {:fn=>"Mark Wunsch", :title=>["Front End Engineer at Scripps Networks"], :n=>{:family_name=>["Wunsch"], :given_name=>["Mark"]}, :adr=>[{:locality=>["Greater New York City Area"]}]}
# => {:fn=>"Mark Wunsch", :adr=>[{:locality=>["Greater New York City Area"]}], :n=>{:family_name=>["Wunsch"], :given_name=>["Mark"]}, :title=>["Front End Engineer at Scripps Networks"]}  

>> m.class
# => Hash  

>> m.to_yaml
# => "--- \n:fn: Mark Wunsch\n:adr: \n- :locality: \n  - Greater New York City Area\n:n: \n  :family_name: \n  - Wunsch\n  :given_name: \n  - Mark\n:title: \n- Front End Engineer at Scripps Networks\n" 

$ ruby -v
ruby 1.8.7 (2009-06-12 patchlevel 174) [i686-darwin10.0.0]