This is one reason why it's important to have a good buddy and easily accessible cutting tools.
In some situations, maybe.
But let me chime in here. Cutting a loose line creates two loose lines (of which neither one probably goes straight to where you want to go) and if one loose line was already a problem then creating two might not be very smart.
The point being that every situation needs to be considered carefully. In my humble opinion, cutting a line is what you do only after you're fresh out of better ideas.
R..