They also come down hard on arson. Why? Because it's really, really easy to get away with arson so they make the punishment really severe to alter the equation. If you got 3 months with probation for arson there would be fires all over the place -- at least that's the calculus.

Same thing with computer crimes. It could have been pretty easy to get away with the data if Swartz had been even slightly clever about it (like not physically returning to the scene of the crime...). It's not as easy to get away with as one might think (see Harvard bomb threat guy), but that's the perception of lawmakers.