"By your logic if I kill your mother, you shouldn't report it because there is a chance the police might investigate a suspect other than me."
And by your logic, revenge so important to you that it is worth risking the death, or lifelong incarceration, of an innocent man.
Of course, I don't expect someone to not report a murder. I'm just playing devils advocate, because your examples are extreme.
Someone took some source code. Valve did NOT need to delay the game. The game would be pirated anyhow. And you know as well as I do that most people who pirate games can't afford them, and most people want to play the game online and Valve's Steam system protects them against this. I'm sure it did not take them six months to modify the key generator. More like a few hours.
So, why is Valve seeking these pirates? Revenge. It's not like someone stole your TV, and you want it back because your insurance doesn't cover it. Nothing was stolen. Data was copied. People may have gotten ahold of some of their "secrets", but the cat's out of the bag.
So this is only motivated by a thirst for revenge. They can get nothing else from this. I'm sure the guy doesn't have much money.
If this happened to me, and I contacted the FBI and they found out who did it, I would drop the charges. I have no desire for revenge. If the person was wealthy I might make them pay restitution, but I'm not going to put a lowly pirate in hundreds of thousands of dollars of debt for taking some source code. If you think that the folks at Valve have never pirated anyhting, then you are a fool. And if they have, then it's pretty damn hypocritical of them to then get mad when someone else does it to them. There is not one person on this planet who uses a PC and has never violated a software license agreement. And the FBI shouldn't be wasting taxpayer money on a small time criminal like this.