I remember struggling with this when I lived in Oxfordshire. The local land owners could'nt stop the ramblers, but could stop the cyclists. So they did, without any good reasoning.
In Norway cycling is as legal on footpaths as it is on the road. Which theoretically means you can ride where ever you want. Bikers for main part, steer clear of popular walking routes though. Its pertty clear which areas are more for pre-dinner strolls, and which are more open to cyclists. There are loads of well maintained trails (partialy graveled) further into the mountians, where you can ride. A few hardcore MTB'rs I know use the antena maintainance roads, which basically point straight up to the highest local peak, and are rarely used.
Personally I think there is a case for some footpaths to bar cyclists, the S.W coastal path in Cornwall as it's very busy with walkers and narrow (would make excellent riding) but if you could cycle on all footpaths people would ride the s.w path and it would be horrid. However most footpaths would be fien to allow riding on, also the thing that anoys me is when you see a bridleways on a map that suddenly changes into a footpath where clearly it carried on but due to historical events it's ended up as a footpath. The evidence required to get a change of status makes it a life times work so is prohibitive.
Personally I think there is a case for some footpaths to bar cyclists, the S.W coastal path in Cornwall as it's very busy with walkers and narrow (would make excellent riding) but if you could cycle on all footpaths people would ride the s.w path and it would be horrid. However most footpaths would be fien to allow riding on, also the thing that anoys me is when you see a bridleways on a map that suddenly changes into a footpath where clearly it carried on but due to historical events it's ended up as a footpath. The evidence required to get a change of status makes it a life times work so is prohibitive.