Graffiti is not something you should do on your next trip to Egypt but old graffiti does tell us a lot. this video clip tells us about Hadrian in Egypt.
Roman graffiti in Egypt - Hadrian - BBC - YouTube: - Sent using Google Toolbar
I know that on the roof at Medinet Habu it says Flo Nightingale and she did visit Egypt, of course we have no idea if she got out a hammer and chisel and carved it herself but it seems unlikely. There is a column at Karnak carved with the name Champoleon and for years I speculated that perhaps the person paid to carve it spelt it wrong. Recently I was corrected by Roger De Keersmaecker who has written 12 books on graffiti, apparently it is a common name in France! www.egypt-sudan-graffiti.be/
Alan Fildes once recomended noting the names and researching them to find out who they were. There is one at the Ramasseum that may have been carved by a wine producer as there is a grape vine and the name and place mention are famous for wine. Perhaps that funded a trip to Egypt. You can find many famous names like Belzoni at this site.
Other graffiti gives you a clue when a tomb was discovered. Covered in Roman or Greek graffiti is was obviously found in antiquity, with dates from travellers on the grand tour it was obviously known about 100-200 years ago
A piece of graffiti at the step pyramid by an ancient Egyptian is actually our only means of known the builder of this pyramid.
None of this means you should leave your mark!!!