This is the only cheapass game I really don't like - the game play just seems wrong.
People have mentioned this before, but it's just too easy to blow up lairs, and there is no reason for not destroying your opponents lairs immediately. Specifically, you only score for capturing spies, which you can only do with a lair. If everyone keeps blowing up your lair cards as soon as you play them, you can never score. Why would you not want to blow up your enemies and stop them scoring?
The only way round this I can see would be a minimum lair size (2 or 3 cards) before anyone can attack that lair.