I've been denied a refund for a game I played for 2 minutes and realized was trash. When I quit it went back to a popped-under splash screen instead of quitting to desktop. I turned off the monitor for the night and the next day when I requested the refund, Steam said I played it for too long and denied my refund.
It was a game under $10 so I didn't lose much but it was still bullshit.