Some waste is worse than others - and unoccupied housing can deteriorate pretty quickly - but, yes, in the context of the stimulus it was something people worried about way too much. A SUPERTRAIN with poorer than expected ridership* might cause you to rethink where you build the next one, but it's still a useful thing to have and at some point population growth will increase the ridership.
*But, yes, we've built plenty of highways to nowhere...
