Then, I do nothing with that knowledge, because it's a weekend hobby and I just enjoy decompiling things. After doing all of this, I wipe out my lab machine and it never sees the network. Now, I decompile, disassemble, and debug your app, taking detailed notes of how it works. I disconnect my 'lab' machine from the network. Say I'm a reverse engineer and I download your app. But as far as I'm concerned (and many others too), reverse-engineering doesn't really become legally enforceable until you've done something with the knowledge. There are some good answers here already, but I wanted to add a few touches.
I used to be a full-time binary reverse engineer, and I still spend about 80% of my time reverse-engineering software (legally).
