Dana Hunsinger Benbow, dana.benbow@indystar.comSeems with all the carousing and partying going on amid the fast-paced cars at the Indianapolis 500 Sunday -- more than 200,000 fans forgot to tweet and Instagram about some important stuff.And if they did, they certainly weren't doing it correctly -- with keywords and hashtags.Case in point: David Letterman had just 50 social media posts about him coming from inside the track at the Indy 500. Just 50 for the co-owner of an IndyCar team and a TV icon who had just performed his last "Late Show" four days before the race.And Letterman was at the race.The data comes from Indianapolis-based Geofeedia, which created geofences around the Indianapolis Motor Speedway Sunday. That's a fancy way of saying the company monitored the social media activity happening in real time at the track.Geofeedia found all sorts of interesting tidbits, such as where inside IMS most of the social chatter was taking place.No surprise. The start/finish line captured 47 percent of social media posts and the Snake Pit 22 percent.But turn 1 was a clear winner with 14 percent of the social media conversation happening there, compared to 3 percent in turn 2, 9 percent in turn 3 and 5 percent in turn 4.As for those mere 50 Letterman posts. Of course, there were more. There had to be more. A guy like that doesn't just walk around at the track in Indianapolis doing interviews, chatting in the garages, taking selfies with fans in the pits and then come away with 50 social media mentions.What likely happened? Many of the posts about him weren't trackable because they didn't contain a keyword or hashtag.It seems Indy 500 fans aren't very good at that. A whopping 40 percent of all posts sent out during the race Sunday didn't contain a relevant keyword or hashtag, according to Karen Hopp, with Geofeedia, a location-based social media monitoring company.So what Geofeedia found relevant to Letterman was simply "a snapshot," Hopp said.Letterman still took the top spot as most talked about celebrity. Actor Patrick Dempsey, who waved the green flag at the Indy 500, accrued 41 posts. Indianapolis Colts punter Pat McAfee garnered 40 posts. Other Indy 500 social media findings:4.6 percent of posts were just photos or videos.Juan Pablo Montoya (@jpmontoya) was the most talked about driver. No surprise, really, he won.The winning team on social from the track was @Team_Penske.And when keywords and hashtags were used? The top ones were: indy500, indy, #indy500, 500, race, speedway, indianapolis, motor, ims, track, Snake Pit, 2015, racing, @IMS 253 and #indycar.