pdo is used for data access -> should be required by egroupware ebuild imho
Does anything not work if the use flag is not enabled? If so please describe the problem and give error messages/logs. emerge --info and "emerge -pvq www-apps/egroupware php" are needed too.
Please re-open the bug after you've provided the requested information.
Scratch that, didn't spot the reporter, sorry...
Please see bug 284536
actually upon checking again i found that Sql FS needs it for the new VFS stuff: http://www.egroupware.org/index.php?page_name=devdocs&lang=&wikipage=SqlFS http://www.egroupware.org/index.php?page_name=devdocs&lang=&wikipage=VFSSystem not sure if a hard dep or some use-flag is better.
The new 1.8 version now depends on php[pdo]