The purpose of a rabbinic decree, which erects a fence around Torah, is to make a rule which will, itself, be treated leniently: Eruvin 58b-59a
Public violation of a rabbinic law is a disgrace to Gd's Name: Eruvin 63a
Creating an edict to keep people from taking a rabbinic enactment lightly: Rosh HaShanah 19a; Eruvin 3a, 68b, 77a, 85b; Bava Metzia 55b
Altering the standard text and procedure established for a bill of divorce [get]: Bava Metzia 55b