A group of bicyclists in the Seattle has filed a lawsuit against the city, alleging that the South Lake Union
Rails embedded in pavement are a long-recognized hazard to bicyclists, as the gap necessary to accommodate the flange of a train's wheels is generally a bit wider than a bicycle tire--making it easy for bikes travelling parallel (or nearly parallel) to the rails to get their tires stuck in the gap, resulting in a crash. There are ways to mitigate this, of course--but in general, the best advice is to design things so bikes cross the rails at a perpendicular angle, not parallel. (Bikes running in the streetcar lane is generally something that ought to be avoided). The best way to mitigate this sort of incident is with dedicated bike facilities, which avoid rails or only cross them in a safe fashion.
Will this suit succeed? My guess is not; government planning agencies generally enjoy immunity (or have only limited liability) for suits of this sort. Were this a case of a motorist suing a DOT or city public works department for an unsafe road, it would be laughed out of court (assuming a lawyer even tried to file such a suit). I don't know specifically what the law is in Seattle, and am too lazy to look it up. :)
But it's important to remember that many things which are beneficial can have drawbacks.