(1) Tired of having to manually add every new cache_* table to your drushrc.php file? What if drush allowed you to just have cache_* in the structure-tables array to include all the cache tables?
(2) drush sql-dump will throw warnings if --structure-tables-key contains some inexisting table names. For instance, if you use the default --structure-tables-key=common and haven't install the search module, you will get warnings for the 'search_dataset', 'search_index' and 'search_total' tables (same for the statistics module).
This patch fixes both issues above by adding support for (1) table name expansion with the * wildcard and (2) removing non existing tables from _drush_sql_get_table_list(), ensuring that all the table names used by sql-dump and sql-sync actually exist.
The immediate benefit is that we could safely bundle drush with a default set of tables for --structure-tables-key=common without the user having to always hack drushrc.php.
First draft patch attached.