Probably that the core bitcoin protocol and network has never been hacked or infringed upon. That alone is quite amazing, and a testament to the good design of the system.
We can imagine that there must be an army of hackers out there trying to profit by corrupting the Bitcoin system. Thus far, they've only been able to successfully attack companies and websites, but never Bitcoin itself.
Because companies, websites, and end users are what hackers target. You don't "hack the internet", you target entities, not protocols. That's how it works. You can't "hack the dollar", but you can take someone else's dollar. You could put one in a color copier, sure. Is that hacking? Ctrl+C on wallet.dat, Ctrl+V. Race to spending go!
When Fort Gox leaves their door open, you don't try to rob the intangible postman who travels at the speed of light. There are hundreds of potential victims right now just begging to fall victim to the irreversibility and anonymity of BTC. I'm sure if some Mr. Teatime wanted to, he could set his watch a few hours late and send some coins around in a circle, or send a fine dust of BTC to random addresses and grind the system to a halt, or stage an incident to isolate the US's internet from everyone else for a period of time for some fragmenty fun. I'm sure he could get the Guild to bump their share up to 51% too. There's not much of a point to it, though, because it would completely destroy the currency and:Money is worthless if one person has all of the money. Money is worthless if no one has any of the money.
I'd say the most compelling statistic is the estimated cost of electricity used in mining.