Ingrid Robeyns has a very nice post at Crookedtimber with an excellent discussion on why "economics should become much more aware of the values it (implicitly or explicitly) endorses. Those values are embedded in some of the basis concepts used but also in some of the assumptions in the theory-building." Her post includes a lovely, brief and clear treatment of the abuse of the Pareto-improvement criterion; it's worth your time to check it out.
However, I worry a bit about the meme that focuses on the lack of clarity about values by economists. For, it reinforces the convenient economist's (and philosopher's) distinction between positive and normative questions, embraced since Sidgwick encouraged the split between the two fields (recall and here). To put the worry more constructively and subtly reinterpret my two earlier posts (here and here) on Raj Chetty's widely discussed NYT op-ed piece: economists are not transparent about their status-quo bias that is embedded in their empirical methodology, which (recall (and here and here), takes important institutions and norms as given).[+] From the point of view of the political economy of economics this (relative) status-quo bias of policy oriented economics is to be expected because the demand for economists is fuelled by existing institutions.