I agree about using the rest of the MS stack with .net but the DB component specifically is highly modular. Let's say you want to go for PostGre or Couch. Neither of those are part of the 'RoR stack' is it? How is is any less correct to use PostGre + .net rather than PostGre + RoR? Is the PostGre + .net community really that much smaller than the PostGre + RoR? I seriously doubt it.