Thanks @Steve.
But I am not sure if it will work in my case.
Imagine a site with authors, that each have their public “author profile page” – where they have som featured posts.
I want to use piklist to have a checkbox saying “feature this post” (which will determine if the post is shown on their author page). So this box is per user, hence I was wondering if ‘field’ => ‘my_featured_post_’+$user_id would be the best approach? Each user would only see their own “feature this post” field.