"Based on your post, it appears that you don't understand how things like statistical significance work. If there is not enough data to make a prediction, you simply should not make a prediction and wait."

Silver doesn't make "predictions", he gives odds. Giving odds implicitly admits that there exists a chance of beating those odds, and attempts to quantify how big or small that chance is. Sure, improbable things happen. That does not make them not improbable. Really, if someone is giving probabilities, you don't just count how many times the lower-probability events happened against him, you take all of his 20% probabilities and look to see whether about 20% of them ended up happening.

Look at it the other way--if all of Nate Silver's "predictions" came true, he'd be way more wrong than if some of them didn't come true, because he's not predicting things with 100% probability! Of all the things he thinks are 70% likely to happen, he's just as wrong if 100% of them happen as if 40% of them happen--he's only right if 70% of his 70% shots happen!