Personally I think running 2 filters on the fuel line is useless. If any particals get by the filter in your tank then by the filter on your lines they they will have a 99% chance of just blowing straight through the engine without causing any harm. These engines are tougher then most people make them out to be... a microscopic piece of debree will more then likley do nothing at all to your engine.

The fuel filter on your pressure line makes sense (which is what you probably see most of the time its not a 2nd filter on the fuel line). The filter on your pressure line will act as a pressure chamber making the pressure to your tank more consistant to give better fuel flow through the fuel lines. I never had a problem with this personally even with a short pressure line but other people seem to.