Spawn killing/camping was a much more prevelant problem in Wolfenstein:Enemy Territory. Many maps had open spawn points that were required to pass through in order to reach objectives.
All that protected the spawning team was a 3-second invulnerability (spawn protection). Many servers enforced a no spawn camping rule but that just caused the attacking team to move their camping back a little and cut off all routes to escape.
My philosophy has always been that, if you allow the enemy to push you back into your spawn, then you deserve it. I've been on both sides of the coin. Good players will usually work their way out of the situation. Its much easier to break out of spawn camping in TF2.