thats the problem, people have no problem bitching about something but a huge problem stopping the problem. if i saw someeone stealing something, be it stupid ass flowers from my neighbors house, and the POS rode up on a bike, you think my 255lbs ass would be afraid to go out and confront some green thumb thief? not a chance, i'd have scared the shit out of him and taken his bike and thrown it into traffic to be run over by a bus.
The only problem with this is the person you confront might be a coward who later comes back to harass your family or mess with your stuff as retaliation. Calling the police seems the better bet if you live right where it happened...