Every action has a predicted consequence — along with side-effects the actor did not dream of (see wikipedia). A few examples:
Railroads forced the creation of a national time-table. Previously, cities kept their own time. New York and Philadelphia could be 5 minutes off, for example, which would disrupt train schedules.
The car gave rise to the current popularity of radio. If not for the car, when else would you be stuck in an enclosed area with nothing to do? At home, the TV clearly dominates.
InstaCalc, a project I’m developing, was developed for an English-speaking audience. However, the calculator interface is inherently multi-lingual (numbers are numbers wherever you go) and much to my surprise, a huge portion of my traffic comes from non-English speaking countries.
Because of these demographics, I had the idea to allow people to write equations in any language. You can write equations in Arabic or Chinese if you like.
Most inventions will have a side-effect you didn’t think of, even taking this law into account :). Keep your mind and design open to change.