I've had several bikes stolen too. But I think violating a fundamental precept of justice, and thereby putting everyone's rights in greater jeopardy at the hands of the police – who have also been way out of control for decades! – is too high a price to pay for discouraging bike theft. Some things actually are worse than the status quo. Requiring bicycle licenses and charging people for them is one of those things, imho.
By choosing not to register their bikes now, people are voting with their feet. You want to ignore their expressed preferences and use the law to force them to register "for their own good", or ? A bicycle registry might be more popular if it were run by, say, the Bicycle Coalition, rather than the SFPD. The police could submit photos, descriptions, and serial numbers of any recovered bikes to the Coalition, or better yet just post them online for the public.
Love & Liberty,
((( starchild )))