The Dixon administration scored a coup this week when it scored a federal grant to expand its pilot commuter water taxi  that now serves Fells Point and Locust Point to Canton.

It's a great idea on some levels. The Locust Point peninsula presents a difficult challenge for surface mass transit. The population isn't sufficient to sustain a rail transit line, and the No. 1 bus  line doesn't have the ridership to secure frequent bus service. Except for the caveats mentioned below, water is the most efficient way to get people to  and  from there to East Baltimore.

But I'm not sure it's a good idea to make it free. You see, free isn't really free. It's fully subsidized. The money has to come from somewhere. But once you call something free, people expect it to remain so and become mightily offended when -- inevitably -- the 100 percent  subsidy is withdrawn. Consider what happened when the Maryland Transportation Authority stopped fully subsidizing people's E-ZPass accounts. Many subscribers reacted as if their first-born child had been confiscated. Perks quickly become viewed as entitlements.

It would put the water taxi on a plane of greater equivalency with other forms of mass transit if the city charged a modest fare once the service expands. It wouldn't have to be a 100 percent recovery of costs. We don't ask any form to  mass transit to do that. But a modest fare -- say $1 to Fells Point and $2 to Canton  -- establishes that the city is providing people with something of real value. It also seems a little unseemly to be providing this service to relatively affluent neighborhoods free when  residents of poorer areas pay $1.60 for a bus ride.

A point for users of the service: Once you pay a fare, you've earned the right to complain. As long as it's free, it's hard to  work up much sympathy with any gripes that  may arise.