Usually run at elevated privileges. I'm going to stop short of a dissertation on OS security but note the ONE BIG THING. If you give me physical access to a machine, I'm in.
As to RAM DISKS, that's something of an non-solution in Unix based OSes. Please look for a RAM DISK for your OS if you must.
I notice the security news that FireWire could be used to bypass your login password because it accesses your RAM.
That got me to thinking: Can you use FireWire to read/write the RAM of the 'puter next to you and could you use this "feature" to turn that RAM into a RAM disk for fast access?