"gnome-screensaver-command -p" is gone in 12.10 so mame can't poke to keep the screen alive. Is there a command I can add before "mame" to deactivate the screensaver and one to reactivate it after I exit "mame"?
If you have installed Caffeine as fleamour suggested, it will do it automatically once you have configured it. This is done by opening Gnome Shell Extension Preferences ([Alt+F2]gnome-shell-extension-prefs[Enter]) and selecting Caffeine in the drop-down menu.
You'll see a switch where you can choose not to display an icon in the top panel, and below that is an empty list. Press "Add Application" and add MAME to that list. It will then activate when you start MAME, and de-activate when you exit the program.
PS: You can also go to extensions.gnome.org in a browser, and get Caffeine and many other extensions there. (Direct to Caffeine: https://extensions.gnome.org/extension/517/caffeine/)
Install Caffeine from Launchpad PPA? Or maybe the official repositories? When activated it will inhibit your screen saver/blanking.