The term "personalized medicine" has been defined by the U.S. Congress as, "the application of genomic and molecular data to better target the delivery of health care, facilitate the discovery and clinical testing of new products, and help determine a person's predisposition to a particular disease or condition." Although the idea is old, in practice the field is still in its infancy. While there has been an enormous progress in terms of identifying clinically relevant polymorphisms in genes for common disorders, this has yet to translate into practical guidelines useful in the treatment of real-life patients.
The article by Rovin et. al. gives a few examples of how personalized medicine might be used in the future. For instance, they describe the presence of a relatively common (up to 11% in white populations) polymorphism in the gene encoding for cytochrome P450 system, required for metabolism of cyclophosphamide into its active form. It is possible that individuals with glomerulonephritis containing this polymorphism could be undertreated when given a standard dose, and perhaps in the future genotyping might allow for more appropriate titration of drug levels.
There are already companies touting the benefits of personalized medicine--for example, the company "23 and Me" offers for a mere $399 the opportunity to have your own DNA analyzed for 117 different traits and diseases, essentially genotyping for a library of several published SNPs which have already been associated with these conditions. Is this useful? Probably not currently--it would be hard to justify using this information on a patient bringing you the results--but there are many who believe that in the future this will be standard practice.