An easy way to find out if its server sided is to start steam in offline mode and try to run the game like that. If steam is already running and you don't want to exit/restart steam or dono how to do that you can always just disconnect your computer from the internet before launching the game (if you are trying this you can test to see if you are disconnected by trying to load a new page in the browser). If the game loads and plays fine while you are not connected to the net then it is not server sided. I was thinking about getting the game myself on payday and if I do I will test it to see for myself.
UPDATE: a friend of mine let me try his copy of the game and i was able to disconnect the network after starting the game and play without network for 10-15 minutes without problems or noticeable changes. therefore I conclude that its not a server sided game. Perhaps the stack size its not shown in an exact value in the memory and I would suggest using greater than/less then last scan.
