We live in a time when it is important to look for ways to save energy. Energy waste in individual homes and offices, albeit minimal, in the long run has a measurable influence on the value of the electricity bill: just think for example to the power consumption in stand-by mode of some of the most common electrical devices such as monitors, printers, televisions, portable DVD, stereo. There are many global initiatives to try to solve this problem, and the Web is one of the main media used for this purpose. Some web-sites, forums and social networks are part of the so-called Social Web, which...