Preserving data privacy is becoming an urgent issue to cope with. Among different technologies, the techniques of perturbation and data swapping offer many advantages, even if preliminary investigations suggest that they could deteriorate the usefulness of data. We defined a set of metrics for evaluating this drawback and carried out a case study in order to understand to which extent it is possible to enforce data security, and thus protect sensitive information, without degrading usefulness of data under unacceptable thresholds.