Pooncrew, I don't mean to be rude but it sounds like you don't know how to use the blockade card. In the description of the blockade card it says (I quote): "Ensure you play it on a territory you will control after attacks have been completed".
So basically, you should blockade a territory (preferably one which protects your bonuses) that is one turn away from your enemy. For example, on the 1v1 ladder if your opponent and you meet up at Siple and Argentina, and they have a stack advantage, ideally you should blockade the South Pole, as it makes Australia and Asia virtually impossible to reach, plus it protects your bonuses.
I understand your point of losing the blockade card when you can't actually use it for it's desired purpose. However, that is sometimes how it works, and I'm sure everyone knows how it feels when a card is wasted. So, I'll give some basic tips on how to use it (bear in mind I am no expert on the blockade card)
* Use it on a territory one turn away from your enemy
* Use it to protect your bonus(es)
* Use it to limit your opponents expansion possibilities
But... most importantly: