It totally depends on what you are doing. You need to take in account if using an ontology will solve any problem at hand. Also you may have an ontological system not build in RDF. At least in what I'm doing, RDF is creating more problems than it solves. Finally there is all the political layer that may go against publishing your data in an open and (web) accessible format and then you need another solution anyway.
To counter the argument of opening data to the outside world, LinkedOpenData has been studied inside companies. I.e opening only inside the walled garden. And guess what? It failed. Simply because companies are not organized so data can "travel" flawlessly. Companies are organized as silos. With boundaries & (implicit) contracts between people, teams, hierarchies.
Of course, everyone knows the information is somewhere here or there, but eventually it is a real hard job to get it for real.
