Galvanic corrosion can be a real problem. You can see it all the time in buildings: plumbing connections of different metals without dielectric fittings, or pipes running through steel stud walls.
For pins holding a blade, it is a very small surface area, so the corrosion would just be where they are actually in contact, After the surface corrosion forms, it protects against further corrosion, as the corrosion/rust is not very conductive. How often have you seen shiny brass pins in a shiny steel hole in a razor? They have a small protective layer of surface corrosion.
With copper scales, the whole length of the blade is susceptible. Granted, the entire length would not be in direct contact with the scales, but where they touch near the spine would very likely be pitted. And every time you would clean the blade, removing the corrosion, a clear path for ion transfer- and more corrosion- would reappear. The acrylic is a very good idea.
If anyone is interested, here is a good link regarding metal compatibility with regard to galvanic corrosion:
http://www.engineersedge.com/galvanic_capatability.htm
Sorry for the boring post.:soapbox:
Matt