Mobygames has been trying to document as many different games accurately as possible. Some of those games don't actually come in a box and are distributed entirely online through direct downloads or from unlock keys. Until recently, the release info for these types of games has usually been the country in which the website was hosted, or the company was based.
This was confusing, so the green light's been given on something else: There's now a new "Worldwide" selection that can be chosen when you're selecting a release date country. Note that this should not be used for traditionally boxed copies of games where different editions (or publishers) may be used for different parts of the world.... even if they release them all on the same day.
So in short, use "Worldwide" release country for games sold online. Feel free to submit corrections to previously approved content in the database to reflect this new standard.