I have numerous sites running Drupal, currently running from a single code base, and using domain aliases to piggy-back the on installation. Drupal then allows a per-domain "multisite" configuration, so that each domain can be customised. The disadvantage, is that all the domains must run under (a) the same subscription (b) aliases of a particular domain, so customers can have their own control panel access (eg. to manage their own email). It would be great if, like the single PHP installation, which all subscriptions access, that applications like Drupal could be installed in a single location, and all subscriptions could access it (perhaps via a symlink?).This makes updating the application trivial (there is only one code base). Since websites have no write-acecss to the original codebase, there is no security issue. All sites still have their own database, and own data storage in their own webspace. If it can be done for PHP, then it should be possible with something like Drupal, ideally with the option to install different versions.
