1. Person A has a laptop
2. Person A no longer has a laptop. Person A did not sell or give away this laptop. The laptop was stolen.
3. Person B now has the missing laptop.
Conclusion: Person B is in possession of a stolen laptop.
2. Person A no longer has a laptop. Person A did not sell or give away this laptop. The laptop was stolen.
3. Person B now has the missing laptop.
Conclusion: Person B is in possession of a stolen laptop.
If you're not doing that, then no, it needn't be.
This guy also has every right to collect and publicize any information collected by the laptop which will help him locate it. He's titled it "This guy has my MacBook", not stole, and he hasn't posted anything irresponsibly that I've seen.
He has every right to collect the guy's personal information, too, but that doesn't mean he can use his credit card or publish his social security number.
Conclusion?