Derick Rethans has a few choice words for those developing PHP packages for linux distributions out there - don't cripple PHP. His example deals specifically with RedHat and their choices on timezone management.
Red Hat thought it'd be wise to create a patch to use the system provided timezone database instead. We (the PHP development team) thought that to be a bad idea because of several reasons. Among them is that it removes control from PHP's users about which database is, decreased performance, and some missing functionality
He mentions other problems - other issues related to timezone support - that caused them to not accept RedHat's patch to try to "fix" things by disabling the bundled timezone database. He looks at why this is such a bad thing, why it can cause trouble with PHP's date handling and what the future holds for this database support (hint: PHP 5.3 will shake things up).