It is possible to steal data from RAM.
In the condition that
- you have external connection to the RAM data and address bus;
- you will have the way that allow all data to be send to data bus of the RAM (Only possible to have a program to do that without affect the system running);
- the program should be running at the same level of kernel;
In short, you have to have a program(or virus or security hole) to be able to steal data from RAM.