These sound suspiciously like homework questions :P. Anyway, by 'virtual life' do you mean an online avatar based social tool, e.g. Second Life? Or social networking sites in general? Obviously they're useful if you're interested in correspondence with other cultures and languages. Not so useful if one becomes so immersed in the 'virtual life' that it takes precedence over 'real life', nothing virtual is comparable to its real equivalent. Bloodninja can attest to that.

Is this your homework? While virtual reality has some benefits, it also has some negative social, psychological and physical effects. Socially, virtual reality is a good forum for people who have difficulty socializing, but there is a danger in encountering untrustworthy individuals online. Physically, too much time spent in virtual environments can lead to obesity, eye strain, seizure activity and increases in electrical activity in the muscles and sweat glands.