I always get angry when my friends (or I) pay for an alignment and are told something is worn out.. because once they move the suspension so that your car drives straight with the worn out piece, when you replace it, the alignment will be off, whereas if you just replaced the worn out piece, it was the "adjustment" the suspension needed.
but as a proper precaution, if you remove, replace or loosen any of the three points on the spindle, you should check your alignment. Generally these three points are the ball joint, strut mount, and tie rod end. That doesn't mean if you know what you ware doing and put it back in the same place that you can't skip the alignment. BUT for the sakes of the forum readers...