No, pg_size_pretty(numeric) was not such a hot idea - Mailing list pgsql-hackers

In 9.1:

regression=# select pg_size_pretty(8*1024*1024);pg_size_pretty 
----------------8192 kB
(1 row)

In HEAD:

regression=# select pg_size_pretty(8*1024*1024);
ERROR:  function pg_size_pretty(integer) is not unique
LINE 1: select pg_size_pretty(8*1024*1024);              ^
HINT:  Could not choose a best candidate function. You might need to add explicit type casts.

The argument for adding pg_size_pretty(numeric) was pretty darn thin in
the first place, IMHO; it does not seem to me that it justified this
loss of usability.
        regards, tom lane