Agree with both. If you are genuinely ill/injured etc then companies should pay a decent rate of sick pay, realistically 100% of your normal rate.
However, you for your part, must be willing to provide evidence to prove you are ill. The first time you are absent for 1 week, or number of separate days accumulating to 1 week, you do not have to provide proof. Any time after this period you will need to provide medical proof/evidence.
This will cut down on all the Monday hangover illnesses etc