I have been using WordPress for a long time, and ever since I always have the problem of integrating WordPress into other content management system (for example, phpbb, etc). The main problem is that many function names in WordPress are not prefixed with 'wp_' therefore conflicting with function names in other existing content management systems out there.
For example, in files wp-includes/functions.php or wp-includes/formatting.php there are several functions defined with and without 'wp_' prefix. Why not add the 'wp_' prefix for all function names so that WordPress can more easily get integrated into other systems.
Please let me know what you think.