Regarding the mass production of random UUIDs, I believe that one would have to provide a seed that was at least 128 bits (or 16 ubyteS) wide in order to have uniform probability of generating any one random UUID from the entire set of 2^128 possible values. (If I read the following web page [http://randomlib.sourceforge.net/html/seeds.html] correctly, there would seem to be a strong probability of collisions when generating more than 2^16 such UUIDs if only a 32-bit seed were used.)
In the same vein, when shuffling playing cards I reckon one would need a 226-bit (or 29-ubyte) seed to cover the entire set of 52! (or approximately 8 x 10^67) possible permutations. It may be that using even more bits is advisable. I wish I understood PRNGs. I don't, but I think the above is true. Thanks to everyone! -- Andy.