Log data is:

  * the largest data source in any enterprise
  * increasingly must be stored for long-term analysis ...
    * by corporate policy or ...
    * by government regulation/demand

Regular open-source tool stacks can't do this without astronomical cost in storage hardware. Various log analysis players have managed to make this data storable and some have done well on the analysis side.

Splunk will do well. I hope this boosts acquisition interest in my old company, http://www.sensage.com, another log analysis company.