i don't think spawn camping is the intended strategy either, being evident from the cases where people get votebanned for it when they do it; and that other servers have a rule against it; or empower people with some sort of spawn-protection. i'm not saying spawn camping is a bug, but it obviously aggravates people and makes people unable to even get out of spawn, no less play the game.
i wouldn't go as far and say it's an intended feature of this game, the great people at valve wouldn't have worked so hard making actual gameplay objectives for this game otherwise.
spawn camping is only a real issue when it escalates; pl_ for example: if your team sucks and the enemy team is good, the enemy team will swarm the entrance of your spawn sooner or later, can you begrudge them for pushing so hard that they have to wait outside your base for you people to respawn? not really. you could give the people being spawn camped some sort of immunity so they can at least leave their base without getting instagibbed before the spawn-door even opens.