I agree to an extent on "reaching" being a myth. It does however come into play if you think there's a mismatch between a player's perceived value and his actual value. If I think Vaccaro is a second-round talent and say, the guard Cooper is a first round talent, but I know Vaccaro won't be around at #39, I take him first and take the risk on waiting to take Cooper. Pedestrian point, but true nonetheless.
Whether I'd be really happy drafting Vaccaro (or Milliner or Banks for that matter) in the first comes down to whether one of Revis/Cromartie are traded. With Revis, Cromartie taking 100 percent of defensive snaps and Wilson on the field most of the time, you can live with average safety play and plug in Allen/Bush/Bell/JAG. If you are downgrading at corner, you really need guys who can help over the top in coverage.