Heh.. If you're normally proportioned (height divided by inseam = 2.0 to 2.2), a production bike should be fine. If you have disproportionately long legs, trunk, or arms, adjusting a production bike to fit (with saddle height, setback, stem height and extension) might not be possible and a custom frame your only option.

I recently got fitted for a custom frame, and the geometry came out to be virtually identical to the production frame I've been riding.