The placed memento's are a point in time but the personal memories / thoughts / respects are the most unforgettable/important things and those things can't be removed .. A little common sense has to be applied otherwise the area will get untidy and fenced off then nobody will be able to access the place and it will be gone. I've been to my grandad's WW2 grave in Italy and placed pic's of my kids there and some personal notes - I don't expect for a second they are still intact or there, the cemetery is immaculate and tended by generations of local families but the memory and respect is. Me and my mates wouldn't consider getting on the grid until we'd said hello to The Fairies.