Most people who crack the program wouldn't buy it anyway. It's cliched, but it's true, I see it all the time. As for shutting down, I'd doubt it (look at all the XDCC channels, etc, on EFNet)
In all honesty, don't try and fight the underground community. Quite a few developers in the past have tried, and all failed, some with varying consequences if I remember right.
As long as you have a trial version, a fair price, and a non-intrusive registration method, and you wont lose TOO many sales over piracy.
