Are Blog Categories Meaningless?

One of the most common things bloggers do is categorize their blog entries.  I am not talking about Technorati or Digg tags or other shared platforms, I mean the ones inside the blogging engines on the individual sites themselves.  ElegantCode.com has more than 20 categories available but what purpose do they serve?  Does anyone really subscribe to category feeds?

My guess is tag provider services offer more value than blog categories.  What do you think?  Are blog categories wasted eye candy?  Should bloggers discard them in favor of Technorati tags?