I find that strategy to be highly annoying. Especially since I usually build hydralisks in masse so I can have a beefy offence to act as my core-defence. Corsairs are really annoying, but I always build spore colonies, because most maps, moneymaps especially, I fear air raids and drops near my main htchery, so I plucker tons of them everywhere, just for good measure. I also usually forget to ascend the overlords speed upgrade, so they're easy Corsair target practice.
