This is for any Google admin on this list:
When you receive a SERVFAIL from a name server listed as authoritative
for a given domain, how long is that negative look-up cached?
When you receive a SERVFAIL from the root servers, how long is that
negative lookup cached?
Does Google follow RFC 2308?
Is there a common cache for all resolvers, or do each resolver in your
DNS server corps maintain a local cache?
When a SOA (when you see one) says 14400 for the minimum TTL (or
negative cache TTL) does Google honor that hold time?