How a Google Headhunter’s E-Mail Unraveled a Massive Net Security Hole
Sloppy work by affected companies since RFC was unambiguous.  But why didn't RFC keep it consistent by requiring verifiers to only work with the same minimum key length?RFC 4871 (sorry for formatting but ipad issue)
 " signers MUST use RSA keys of at least 1024 bits for
   long-lived keys.  Verifiers MUST be able to validate signatures with
   keys ranging from 512 bits to 2048 bits, and they MAY be able to
   validate signatures with larger keys.  Verifier policies may use the
   length of the signing key as one metric for determining whether a
   signature is acceptable.   Factors that should influence the key size choice include the
   following:

   o  The practical constraint that large (e.g., 4096 bit) keys may not
      fit within a 512-byte DNS UDP response packet

   o  The security constraint that keys smaller than 1024 bits are subjec to offline attacks..."