Right now, activating a plugin that causes a PHP fatal error means that you have to fire up FTP and delete the plugin file, which is cumbersome and technically intimidating for some people.
Upon plugin activation, we should conditionally load the plugin the user is activating, and only if it loads with no issues will it actually be activated.
Idea 1: (simple) submit a nonced form with the plugin file name, verify the nonce, and include the plugin. On footer/shutdown, activate the plugin. If there is an error, it won't be activated.
Idea 2: (sexy) Conditionally include the plugin in an AJAX request. If you don't get a valid response, shoot back the error in a dialog or on-page error box. Revert to 1 for JS-less people.