Using a secure RNG is always a good idea, unless you know you need lots of (predictable given the seed) random numbers for example in Monte Carlo sampling.
Even in randomized algorithms you may have to be careful what RNG you use, because of DDOS risk. For example see the problems with Python and Ruby hash tables that could be exploited to have worst-case behavior because their behavior was entirely predictable.
In a MMO you most certainly want to use a secure RNG, as cheating is rife in them. If a player can get an advantage by predicting the RNG, someone will.
Even in randomized algorithms you may have to be careful what RNG you use, because of DDOS risk. For example see the problems with Python and Ruby hash tables that could be exploited to have worst-case behavior because their behavior was entirely predictable.
In a MMO you most certainly want to use a secure RNG, as cheating is rife in them. If a player can get an advantage by predicting the RNG, someone will.