the hordes of japanese and korean tourists who swarm off endless lines of buses, troupe as quickly as possible to the postcard photo-op, take snapshots of each other in front of, or climbing whatever attraction they are visiting, make lots of noise, and troupe out, not spending a dime on the local economy, since they come in japanese or korean tour buses, stay at japanese or korean hotels, and eat in the restaurants and shop in the souvenir shops within said hotels. everything but the fees they pay the cambodian government goes straight back home.
plus they make it very difficult to get a good photograph of the tomb raider temple ;p