Behavior should either be an 'only root can do that' error or (preferable to me) the list of source URLs you get for the same command as root.
Are you root?
"emerge -pf package" works fine for root. However, when the same command is executed by non-root, it throws a bunch of error messags. My thought is that, because it is a "pretend" command, it should work for non-root. Or, if it is decided that the command shouldn't work for non-root, it should gracefully exit with a meaningful message (along the lines of 'root access required'. Admittedly, a minor point.
Add user to the portage group.
Change for 2.0.47 series.