gistfile1.rb

ree-1.8.7-2011.03 :147 > k = User.first.kbadges.find_or_create_by_title(:title => 'Foo', :variant=>"collectible", :badge_type=>"newbish", :description=>"Fashion gems are fashion!", :grant_activity_date=>"2009-10-28 08:02:29 UTC")
 => #<Kbadge id: nil, user_id: 1, title: {:variant=>"collectible", :badge_type=>"newbish", :description=>"Fashion gems are fashion!", :title=>"Foo", :grant_activity_date=>"2009-10-28 08:02:29 UTC"}, description: nil, variant: nil, badge_type: nil, badge_count: 0, grant_activity_date: nil, created_at: nil, updated_at: nil> 
ree-1.8.7-2011.03 :148 > k.title
 => {:variant=>"collectible", :badge_type=>"newbish", :description=>"Fashion gems are fashion!", :title=>"Foo", :grant_activity_date=>"2009-10-28 08:02:29 UTC"} 

class Foo < ActiveRecord::Base
attr_protected :bar
validates_presence_of :bar
end

ruby-1.8.7-p334 :003 > foo = Foo.find_or_create_by_bar(:bar => "BAR", :foobar => "FOOBAR")
=> #Foo id: nil, bar: nil, foobar: "FOOBAR", created_at: nil, updated_at: nil>

Sí, solucionado con usar la sintaxis de bloque para los atributos. Gracias mil.