It's 2am you are standing on Dupont Circle (DC) trying to hail a cab back to Silver Spring (MD) to go home after a night of utility maximizing. A cab approaches, the cabbie asks where to? You say Silver Spring. The cabbie says no and drives off.
It happen to me last year and it happen recently to the blogger at Sprung on the Spring (a local Silver Spring blogger). As the their post describes even though it is illegal to refuse service, several DC cabs refused to go to Maryland. They don't want to go to Maryland, because DC cabbies legally can't pick up new passengers in Maryland. I think this shows that a law change is unlikely to solve the problem of getting a cab from DC to MD after the bars close.
So I propose two solutions. Granted this will be theoretical, since with a 7 month old I can't do the empirical research necessary to test these theories. If you find yourself in a similar situation please let me know if either of these work.
Solution #1: Instead of saying I'm going to Silver Spring. Start by saying $50 for a trip to Silver Spring (sure it's double the price), but given these two data points $25 is a small price to pay for not trying to hail cabs between 2-3am. I think the cabbie would go for it, since it should compensate them from missing one fair. I also find the negotiations are quick between the cabbie and the person trying to hail the cab. You basically get 1 shot.
Solution #2: Take me to Alaska and Georgia Ave! This is the border of Silver Spring and DC. Once there try to negotiate for the last mile or two if you live in downtown Silver Spring. If the cabbie doesn't go for it, get out hail another cab. A new cab picking you up there is unlikely to refuse service. I'm not sure how many cabs are going by there but I assume it's a decent amount.