Last week, Mark Zuckerberg, the Facebook founder and CEO, announced that his company was to launch a new email messaging system. He wasn't seeking to elbow in on free email services. This service would be "something different". Traditional email is made for intermittent exchanges of content, he explained, whereas this new messaging medium will support "ongoing conversations". ... In a world where we already have emails, texts, instant messaging, video conferencing and mobile phone calls, it could lead to communications overload.