Can't use "any" with SQL functions

Is there a reason we disallow using "any" with SQL functions?

decibel(at)phonebook(dot)local=# create function textcoalesce("any") returns
void language sql as $$SELECT coalesce( $1::text, '<NULL>' )$$;
ERROR: SQL functions cannot have arguments of type "any"
STATEMENT: create function textcoalesce("any") returns void language
sql as $$SELECT coalesce( $1::text, '<NULL>' )$$;
ERROR: SQL functions cannot have arguments of type "any"
decibel(at)phonebook(dot)local=# SELECT version();

version
------------------------------------------------------------------------
-----------------------------------------------------------------------
PostgreSQL 8.3.7 on powerpc-apple-darwin8.11.0, compiled by GCC
powerpc-apple-darwin8-gcc-4.0.1 (GCC) 4.0.1 (Apple Computer, Inc.
build 5370)
(1 row)

decibel(at)phonebook(dot)local=#
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Decibel!, aka Jim C. Nasby, Database Architect decibel(at)decibel(dot)org
Give your computer some brain candy! www.distributed.net Team #1828