It shouldn't be dangerous. Why you think it can be dangerous?

Btw: Your function showAuthorPosts could be better. Instead of getting the id manually declare the route with an id. Like this:

Route::get('user/{id}', function($id)
{
return 'User '.$id;
});

see also on: http://laravel.com/docs/routing#route-parameters

or

Route::get('authorsorwhateveruri/{id}', 'PaymentController@showAuthorPosts');

public function showAuthorPosts($id)
    {
        // $id = Request::segment(3); not needed.

        if(is_numeric($id)) {

Though im not sure if you can chain it with a ->where('id', '[0-9]+');
Then you would not need to check if numeric.

You are right it's possible:

http://www.laravel-tricks.com/tricks/routing-patterns