Critics say big pre-IPO investments overvalued the company
                                
                                
                                    (Newser) -
                                    With Groupon having lost three-quarters of its IPO value, several of its key early investors, including web icon Marc Andreessen, have left the building, reports the  Wall Street Journal . Andreessen's firm, Andreessen Horowitz, invested $40 million of the $950 million pumped into Groupon in the months before  it went...