Here's a more useful one:

Variance means that even with less than 51% of the hashing power you have a chance, albeit a smaller one, to disrupt the chain. For example, a bunch of people freaked out some weeks ago because the Bitcoin chain managed to get... I think it was like 3 blocks in a 10 second period? People also often freak if there's the occasional hour between blocks, but this has happened MANY times without a drop in hashing power.

Think of it this way: Take, say, a d12 for roll playing, and assume you and several players are sitting at a table, and to "win" the game you have to roll a 1. The average chance of you rolling a 1 is going to be 1 in 12, but...

You could roll that 1 result twice in a row, or, you could get 24 rolls in a row... that come up with a different number. In a large enough sample set, with a truly balanced die to roll, it'll just about always be "even" among the different numbers, but if you're looking at just a few rolls in a row...

If you play many games with dice, cards, etc, it only takes a moment of pondering that before you can realize that if you were to roll that die 12 times, it's quite possible for you to _NOT_ get each number exactly one time.

Now imagine the block chain lottery as rolling a die with 115792089237316195423570985008687907853269984665640564039457584007913129639936 sides... (Someone correct me if I'm remembering wrong and it's not a 256 bit hash in use, please.)