We examine a popular decoupling strategy for separating functional molecules from metal surfaces, using the molecular switches azobenzene and TBA as examples. Our combined experimental (Normal Incidence X-ray Standing Wave method) and theoretical (Density Functional Theory) study demonstrates that purely structural arguments to predict the functionality of adsorbed molecules have to be taken with much care, as they may turn out to be deceptive. (C) 2010 Elsevier B.V. All rights reserved.