This time of year, you will see a dozen guys each weekend riding technical mountain bike rides like Hall Ranch, Walker ranch, and white ranch on cross bikes.
You don't hit the rocks like you can on a DH rig, but I can clean hall on a cross bike, and my PR
for a complete climb up, upper loop, and descent is 1 min 15 sec faster on the cross bike than the XC full suspension rig..
(Transalation: The faster climbing speed offsets the slower downhill speed, since I'm not a gonzo DH guy anyway).
The won't fold, but you don't willy nilly drill them in the rock gardens..