[eluser]Michael Wales[/eluser]
Create a route for all of your named methods (the ones in which you know exist). The last route in your routes.php file should point towards the user-handling method().
Since routing works from top-to-bottom, all of your known controllers will be picked up by their respective routes and anything left over will be picked up by the user handler.
Example: The following will forward any requests for blog/(number) to the correct controller and anything else will be forwarded to the user controller (to display a profile or something).
Code:
$route['default_controller'] = "home";
$route['scaffolding_trigger'] = "";
$route['blog/(\d+)'] = "blog/view/$1";
$route['([a-z]+)'] = "user/view/$1";
Note: Don't quote my regex, I really suck at it.