Properties of some double-chained surfactants which form spontaneous thermodynamically stable unilamellar vesicles in water are reviewed and analysed in terms of current ideas on self-assembly and recent direct force measurements. The reasons for the apparent success of older theories are discussed. The conclusion is that the older description in terms of primitive model double-layer theory, van der Waals, and additional hydration forces has to be abandoned for a rigorous theory of self-assembly. That conclusion does not abrogate the usefulness of the present theoretical framework in providing a predictive rationale for many systems and in biological problems. This is illustrated by the use of cationic surfactants as immunosuppressants, bacteriocides and other applications.