People have mostly said it. Scirra has a number of things going for them, including relatively low price point, crazy good customer support, constant updates, powerful free version, licensing for certain commercial uses (no need for commercial for your first $5K!).
So, there's no real need to pirate the software, since in Scirra's case (unlike EA or others) you get way better support with the official product than from the pirates. You only "need" a pirated copy if you get around to using more than 100 events, OR if you already have the personal license and you wind up earning more than $5K off it ...
... which you can't get away with since Scirra will spot your pirated license on your widely-known commercial work.
C2's about as pirate-proof as it gets, and while pirating it is unequivocally wrong, it frankly probably results in better advertising and future sales through publicity than it "costs" from the initial act. Why?
If you pirate it because you weren't going to buy it anyway ... and you can't make money off a pirated copy because you'll be instantly busted ... what's the point? And does that person *really* hurt Scirra? Meh. If that person winds up falling in love with the toolset and wants to make money, they'll have to buy the license.
Then you have people like me. I'm in a position myself where I was able to buy the personal license and reasonably expected to need more than 100 events, etc. I don't know if I'll make more than $5K off anything I make with C2, but when it went on sale I sprang for the business license out of a sense of optimistic exuberance and dangit, because Tom and Ashley are just the sort of people I want to support.
Part of the brilliance is C2's price point. Take Adobe CS6: yes, it's ridiculously powerful and magical ... it's also almost cartoonishly expensive. There's a price above which people don't even have a conception of affording. For *most* people, $676 for even that powerful a tool is unthinkable. It's possible that for Adobe, they could actually make more money with a lower price by opening it up to a wider audience. C2 Personal, on the other hand, is $119 (not cheap, but not much more than two AAA games) and gets you the full program, and you don't even need to buy the commercial version unless you've already made $5,000!
If you're at all thinking about using C2 commercially, the first $119 is a no-brainer investment (a serious one, but fair and realistic), and if you weren't going to pay that for this sort of kit, you weren't going to pay anything. Scirra doesn't lose.