This is still a problem on Ubuntu 14.04.1 with puppet 3.4.3 and facter 1.7.5.
Interestingly, on Amazon Linux 2014.09 with puppet 2.7.25 and facter 1.6.18, the EC2_* facts are present.

The latest version of the gem appears to have completely refactored the ec2.rb facts: https://github.com/puppetlabs/facter/blob/master/lib/facter/ec2.rb

The latest 1.7.x gem release is still broken: https://github.com/puppetlabs/facter/releases/tag/1.7.6d

The 1.6.18 gem has the same broken ec2 code: https://github.com/puppetlabs/facter/releases/tag/1.6.18

Looking at the amzn1 source rpm, it appears Amazon is patching the facter gem when packaging it:
https://alami-source-request.amazonaws.com/cgi-bin/source_request.cgi?instance_id=i&region=us-east-1&version=2014-09-0&srpm_name=facter-1.6.18-7.25.amzn1.src.rpm

rpm2cpio - < facter-1.6.18-7.25.amzn1.src.rpm  | cpio -idmv
      0001-19989-Filter-virt-what-warnings-from-virtual-fact.patch
      0002-976942-correct-ipaddress-non-loopback.patch
      0003-ipaddress-parsing-net-tools.patch
      0004-FACT-480-Remove-current-directory-from-Ruby-load-path.patch
      facter-1.6.18-ec2-vpc.patch
      facter-1.6.18.tar.gz
      facter-1.6.18.tar.gz.asc
      facter.spec

FILE: facter-1.6.18-ec2-vpc.patch
      diff -up facter-1.6.18/lib/facter/ec2.rb.vpc facter-1.6.18/lib/facter/ec2.rb
      --- facter-1.6.18/lib/facter/ec2.rb.vpc 2013-03-13 18:17:44.000000000 +0000
      +++ facter-1.6.18/lib/facter/ec2.rb     2013-05-09 18:04:10.000000000 +0000
      @@ -28,8 +28,7 @@ def userdata()
         end
       end

      -if (Facter::Util::EC2.has_euca_mac? || Facter::Util::EC2.has_openstack_mac? ||
      -    Facter::Util::EC2.has_ec2_arp?) && Facter::Util::EC2.can_connect?
      +if Facter::Util::EC2.can_connect?
         metadata
         userdata
       else
      diff -up facter-1.6.18/lib/facter/util/ec2.rb.vpc facter-1.6.18/lib/facter/util/ec2.rb
      --- facter-1.6.18/lib/facter/util/ec2.rb.vpc    2013-03-13 18:17:44.000000000 +0000
      +++ facter-1.6.18/lib/facter/util/ec2.rb        2013-05-09 18:03:26.000000000 +0000
      @@ -35,6 +35,7 @@ module Facter::Util::EC2

           # Test if the host has an arp entry in its cache that matches the EC2 arp,
           # which is normally +fe:ff:ff:ff:ff:ff+.
      +    # WARNING: This does not work in VPC as VPC hosts have real MAC addresses
           def has_ec2_arp?
             kernel = Facter.value(:kernel)








## From Amazon Linux 2014.09 in VPC:
curl http://169.254.169.254/2008-02-01/meta-data/instance-id
           i-2b54b1cb

curl http://169.254.169.254/2008-02-01/meta-data/ami-id
           ami-b66ed3de

facter -d metadata
           value for lsbdistid is still nil


FILE: /usr/lib/ruby/site_ruby/1.8/facter/ec2.rb




              # Test if the host has an arp entry in its cache that matches the EC2 arp,
              # which is normally +fe:ff:ff:ff:ff:ff+.
              # WARNING: This does not work in VPC as VPC hosts have real MAC addresses
              def has_ec2_arp?
                kernel = Facter.value(:kernel)

                mac_address_re = case kernel
                                 when /Windows/i
                                   /fe-ff-ff-ff-ff-ff/i
                                 else
                                   /fe:ff:ff:ff:ff:ff/i
                                 end

                arp_command = case kernel
                              when /Windows/i, /SunOS/i
                                "arp -a"
                              else
                                "arp -an"
                              end

                if arp_table = Facter::Util::Resolution.exec(arp_command)
                  return true if arp_table.match(mac_address_re)
                end
                return false
              end

          ...
          ...

          if Facter::Util::EC2.can_connect?
        metadata
        userdata
      else
        Facter.debug "Not an EC2 host"
      end


## From Ubuntu 14.04.1 in VPC:
curl http://169.254.169.254/2008-02-01/meta-data/instance-id
           i-854ca965

curl http://169.254.169.254/2008-02-01/meta-data/ami-id
           ami-9eaa1cf6

facter -d metadata
           Not an EC2 host


FILE: /usr/lib/ruby/vendor_ruby/facter/ec2.rb

              # Test if the host has an arp entry in its cache that matches the EC2 arp,
              # which is normally +fe:ff:ff:ff:ff:ff+.
              # WARNING: This does not work in VPC as VPC hosts have real MAC addresses
              def has_ec2_arp?
                kernel = Facter.value(:kernel)

                mac_address_re = case kernel
                                 when /Windows/i
                                   /fe-ff-ff-ff-ff-ff/i
                                 else
                                   /fe:ff:ff:ff:ff:ff/i
                                 end

                arp_command = case kernel
                              when /Windows/i, /SunOS/i
                                "arp -a"
                              else
                                "arp -an"
                              end

                if arp_table = Facter::Util::Resolution.exec(arp_command)
                  return true if arp_table.match(mac_address_re)
                end
                return false
              end

          ...
          ...

      if (Facter::Util::EC2.has_euca_mac? || Facter::Util::EC2.has_openstack_mac? ||
          Facter::Util::EC2.has_ec2_arp?) && Facter::Util::EC2.can_connect?
        metadata
        userdata
      else
        Facter.debug "Not an EC2 host"
      end