There's no commuter tax in DC, but it comes up again and again to help account for the large shortfalls of revenues to the city. Like other cities, there is a large number of folks who work here but live outside of the city limits (about 70% of the District's workforce).
The biggest problem DC faces, in my opinion, is the huge amount of non-taxed entities that work in and utilize the city (federal government, any international governments, etc). It's a significant revenue loss -- 42% of DC real estate is federally owned and hence tax free; 11 % is owned by embassies, nonprofit groups and others exempted from taxation, city officials say. That's more than half of the commercial real estate in the city.
There have been commuter taxes been in other cities (such as New York). There's some form of commuter tax in 41 states because cities where people work have to pay for the services used by employees (police, fire, emergency, transportation infrastructure, etc). Commuter taxes are not uncommon, but there has been a ban instituted by Congress for D.C. only.
Taxes for commuters do not increase, by the way. The apportioning among the jurisdictions changes.