In some email I received from Ken Hornstein, they wrote:
[...]
> 
> I am amused by the comment that said (paraphrased) "BSD error semantics caused
> DNS queries to dead nameservers to slow down", when there is code in the
> BIND client code that specifically does a connect on a UDP socket when only
> one nameserver is being queried.
> 
> --Ken
> 

I think this is a response to the latest versions of BIND having trouble
with Linux due to it reporting errors on unconnect()'d sockets whereas
BSD doesn't.

darren