iserith
Magic Wordsmith
I would say that railroading is always bad because by definition it involves force via subverting choice a player believes he or she made in good faith; however, if a player agrees to choose certain things over others (e.g. follow the plot of the module everyone agreed to play to the exclusion of choices that aren't on that plotline) or agrees the DM should, say, engage in the illusion of choice for whatever reason the group agrees is acceptable, the DM is not railroading since the DM is not forcing those outcomes.