Or anyone in responsible position, for that matter.
Imagine if someone hacks into Shashi Tharoor's twitter account and posts something inflammatory, like say, "India plans to nuke Pakistan" or "All muslims should be killed" or some such thing. It is quite likely that it will be taken at face value by many people, including those in power in other countries. Pretty soon situation may get out of control leading to serious consequences. One could say, "oh it is the others' mistake if they jump to conclusion without verifying the authenticity of the comments", but then, given that he is known to have a Twitter account, you can hardly blame others for taking comments on it seriously. So what it does is to give some engineer sitting in Twitter office the power to change the course of an entire nation. And he has that power, because someone in a responsible position thought it fit to use the services provided by some little American company to communicate his thoughts.