What are the disadvantages with using a compass?

A compass is made to point at relative north not exact north. Relative north is a place inGreenland where there is a strong magnetic pull, and because of weathering and changes in the earth it moves every so often. Exact north is in outer space and is the north star. However it is obviously not magnetic therefore there are not magnetic compasses that point to exact north. Digital compasses such as ones you could find on cell phones or other GPS devices are probably the best thing to use if you are trying to go exact north otherwise a regular compass is good enough for directions and scouting.