I've never run a marathon, but I've run a half marathon...and I'll tell you, ANY extra encouragement is needed. I remember how awesome it was to see random people alongside the roads in downtown St. Pete cheering us on when I was running the St. Pete Rock N Roll Half Marathon. It DEFINITELY helps! See this little kid holding up this sign is soooooo awesome.
A kid was holding a Super Mario Bros sign saying "TAP HERE TO POWER UP" for the runners during a marathon, and you can see a lot of the runners tapping it! I totally would have too!!