How often have you accidentally pressed ctrl+s and had your terminal frozen? I don't understand this default mapping at all. It should be gone from Linux installations. If you're a newbie you might have even thought that the terminal has died (I did think so, and I'd restart the terminal when that happened). Apparently you need to press ctrl+q to unfreeze the terminal. These keys could be used for something better than freezing and unfreezing the console.
Get rid of these keys by running these commands:
stty stop undef stty start undef
Instead remap these combinations to something much more useful.