Nice bugs that no one seems to want to fix:-

mysql> create table test5 (
wibble varchar(500), PRIMARY KEY (wibble)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
ERROR 1071 (42000): Specified key was too long; max key length is 767 bytes

mysql> create table test5 (
wibble varchar(500), PRIMARY KEY (wibble)
) ENGINE=myisam DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
ERROR 1071 (42000): Specified key was too long; max key length is 1332 bytes

And even with MySQL 6.0.9 (using the Falcon engine which is still brand new)

mysql> create table test5 (
wibble varchar(500), PRIMARY KEY (wibble)
) ENGINE=falcon DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
ERROR 1071 (42000): Specified key was too long; max key length is 1100 bytes