I like these a lot, and would like to use them for everything. Why would doing RDF triple stores for everyday programming (Entities/Tables), such as Contacts, Customers, Company etc. be a bad idea.
Are there short falls in the technology that I have not come across. I was concerned about retrieving data, but I think this is covered with SPARQL.
There are no one-size-fits-it-all tools. Triple stores are appropriate and usable today for some kinds of tasks and not for others.
A similar question was asked on semanticoverflow.com and the common answer was the same: “use whatever is appropriate”.