Micheal Swan believes after prepositions of place, we often use a personal pronoun (me, you etc) if the meaning is clear without a reflexive. Compare:
(1): She took her dog with her. (NOT ... with herself.)
(2): They divided the money among them. (NOT ... among themselves)
(3): Close the door behind you.
However, I wonder why the following, although using a prepositions of place, is correct:
(4) He placed his little dog beside himself on the couch.
As a matter of fact, I don't know where we cannot use reflexive pronouns.