Unless they've been keeping a list with such information as they've been adding/updating drivers (which is extremely unlikely) then they're not going to know. The only way they would be able to find out is by loading up the game and noting how much memory it's allocating. They may have general ideas of how much each driver wants, but that would only be for a small subset and would not be accurate enough.
The VMM settings are stored in a plain text file which can be updated and re-distributed so as to avoid downloading a new, recompiled binary.
Furthermore, end-users will be able to manually force VMM settings for games that are not supported OOTB. If you come across a game that did not make the initial cut, you can fiddle with the options until it loads and then add the information to the text file.
I'm asking people to report OOM games because I'm offering to setup as many as possible before the new release. If people don't want to take the time to note them, then they'll have to fiddle with them themselves instead of having something that "just works".
Also note, however, that if too many people just blindly add games to the database as "out of memory" without actually checking them, then I may become frustrated and just stop adding game settings to the VMM file. So think and test carefully before you decide something like, "I really want this game to work - I'll just add it to the list, willy-nilly."
