WTOP provided an informative piece on their website discussing this phenomeneon and listing the hit and run crashes in the District of Columbia and surrounding Maryland suburbs this year. http://www.wtop.com/?nid=41&sid=2589790
The majority of the incidents have been discussed here before and the solution put forth by a AAA spokeperson, "prosecution of the drivers" while obvious and appealing, is easier said than done. Most of these incidents take place at night outside the presence of witnesses and one suspects that the drivers in many instances have been drinking or using drugs and do not wish to be apprehended under any circumstances especially if intoxicated.
In many instances the sheer force of the collisions leaves evidence behind that can often identify the hit and run vehicle but of course not the driver. In some instances there even appears to be evidence that the crashes are intended. http://www.maryland-law.com/blog/fatal-dc-pedestrian-hit-and-run-crash-intentional.cfm
There seems to be no magic bullet solution. Better cooperation between authorities and area drivers would help and one would think that the prevalence of red light and other cameras might provide evidence but the bottom line is that area pedestrians and bicyclists out at night on under illuminated roads are at their own peril.