In Search of the Next Next-to-MSSM
  It is argued that the Next-to-MSSM (NMSSM) is unnatural from the point of view of cosmology and fine tuning. In particular, such singlet extensions to the MSSM do not provide a simple solution to the `$\mu$-problem'. Models with singlets can be constructed using gauged-$R$ symmetry or target space duality. However their superpotentials have terms in addition to those of the NMSSM. 
S.A.Abel