Cities in the Greco-Roman world were absolutely rife with graffiti. No subject was too large or too small for these people to share their thoughts about it in a public space — from imprecations to the gods to notations on the price of cheese. You found graffiti in temples and garrisons, living rooms and latrines. Everyone was at it.
See the above link for full story–it sounds like not alot has changed in 3000 years of graffiti despite the seriousness of archaeological analysis.