I hear many models for particle interactions described that use gravitons, virtual particles, and that reference many concepts that I thought were highly controversial; but these models don't seem to be treated as such. Mainly though the question of gravitons is what attracted me. If we have no quantum theory of gravity, then how can we effectively use these models? How can we know the nature of a graviton? Clearly any theories of Quantum Gravity fail thus far. Aren't we virtually assured that our models are incorrect since we can't produce a theory?