What do you mean by a "good" PRNG ? I think what we understand to be good here might have to
change. It's one thing for a PRNG to generate a sequence of numbers with good statistical
properties and which doesn't repeat its inherently predictable sequence until a very large
integer number space is exhausted. It's entirely another to have a PRNG with a published
algorithm and an attacker able to obtain prior information relevant to its internal state but
provably unable to predict the subsequent sequence of numbers generated. The P here means
pseudo, because the randomness isn't randomness at all - it means that the sequence of numbers
is generated using an algorithm and not a noise source. Certainly the developer and
administrator can attempt to reseed such an algorithm periodically and cryptically. The issue
is how much can an attacker learn by knowing previous numbers in the sequence in order to
predict subsequent numbers in the sequence.
One solution for the paranoid is to use /dev/random instead of /dev/urandom as the entropy
source. This is a good idea when generating cryptographic keys intended for medium-long term
use, but running a DNS recursive resolving server which needs to generate thousands of
unpredictable source port numbers and transaction IDs a second is going to need a faster
entropy source than /dev/random hence the need for a PRNG in the first place.