The big difference between anonymity in the 90's and today is scale. Today our networks reach billions of people most of whom, to put it as politically correctly as possible, aren't very sophisticated. I am not talking about education levels. Everyone has weaknesses. Wether its the guy on wall street, silicon valley or McD. It is not a question, of whether their weaknesses will be taken advantage off. This is happening already at a scales never seen before. Whether it is our stock market bubbles or rise/fall of companies overnight or the rise/fall of political leaders/movements overnight or Snooki, Paris Hilton or Gangnum Style, network effects effect everyone in highly unpredictable and uncontrollable ways. Anonymity is a catalyst.
Social networks turn into outrage factories at the drop of a hat these days and we definitely need control rods to atleast slow things down. Anonymity is an obvious candidate.