Recent results suggest that surface-enhanced Raman Spectroscopy (SERS) of single adsorbate molecules is possible under appropriate circumstances. We propose that this phenomenon is associated with very intense enhancements available at interstitial sites (hot spots) of nanoparticle assemblies (either colloid particle aggregates or rough surfaces) illuminated with light of an appropriate wavelength so as to excite surface plasmons, coupled with additional resonance enhancements due to a judicious choice of ad-molecule. The former contribution, known as electromagnetic (EM) enhancement, has been known for years to be capable of producing EM hot spots where the enhancement can top 1011. This fact seems to have been rediscovered recently. It is also known that the fields at the surface of fractal aggregates commonly show hot spots. These are also, at times, capable of such high local enhancements. On fractals, the location of these hot spots are, however, highly dependent on parameters such as the excitation wavelength. In contrast, small compact clusters (when properly designed) have the benefit of a wavelength-independent hot spot where a small number of molecules could be (chemically) directed and detected. This insight suggests an eventual optimally engineered single-molecule SERS system with predictable enhancement capabilities and optimal adsorption (i.e. chemical) characteristics at the hot spot.