And the rebuttal, of course, is that there isn't any one single place to choose the default. ANY application that can be the default MAY (and usually does) include a setting to make it the default. A polite application, like most of Apple's, will allow you to set the default to some other app.

For example, Mail and Eudora would both let you set your default mail program, but Eudora would only let you set it to Eudora. Mail lets you choose from among all currently installed apps that support the mailto: protocol.

Similarly, almost any web browser offers a setting to become the default web browser, but Safari (and perhaps a few others) will offer to abdicate in favor of any currently installed app what will respond to http: URLs.