So when you have your retirement based on 3 or 4 stocks and one of them is Enron or Nortel how do you manage that scenario?  While fortunately those types of cases are relatively rare, both of those stocks would have been quite at home in the list of examples prior to their demise.

The optimum number of stocks will vary from person to person based on their personal circumstances, portfolio size, investment interest level, and overall objectives.  But in my opinion if an individual can't keep track of 3, 4, or a maximum of 6 stocks they probably shouldn't be investing in individual stocks on their own. 

I personally manage over 50 different investments - admittedly not some thing that most people will want to do.  But for my level of interest and objectives it works.  But for most people I would say that somewhere between 10 and 25 would be a starting point in the discussion.