This [roadkill] is a relatively new source of fatality; and if one were to estimate the entire mileage of such roads in the state, the mortality must mount into the hundreds and perhaps thousands every 24 hours." (Joseph Grinnell, 1920) found on wildlifecrossing.net.
Crowd sourcing has yet another use. It turns out that there is significant scientific interest in roadkill. For example,
Over the last few decades, Eastern Fox Squirrel have been migrating from their original sites of invasion in California (Bay Area and Los Angeles) toward other areas, where they tend to displace the native Western Grey Squirrel. Because these two species are commonly-reported as roadkill, we can study their co-distribution and where Eastern Fox Squirrel have successfully invaded or are invading the habitat of Western Grey Squirrel. As you can see from the map below, there are several areas where only Eastern Fox Squirrel or Western Grey Squirrel occur and other areas, such as Sacramento, Santa Cruz, and Monterey Bay where both species occur. These mixing zones may indicate active invasion by the non-native species. (CROS Annual Report)
Knowing the locations of roadkill hotspots will also allow researchers to recommend best practices for road builders.
The states of California and Maine are now using an online reporting tool to track road kill. Anyone in those states can report identifiable roadkill using a web interface at http://www.wildlifecrossing.net/california/node/add/roadkill (registration required).
Is there an app for that? Turns out that the plans are in the works for one.