More private garages that accept bikes would go a long way towards mitigating the problem. They've just started appearing here in NYC (the muni garages are/were free, but maintenance and sanitation seemed like major issues) so I've started using them. I've been using Parkfast (http://www.parkfast.com/) for about 6 months and have been very happy with them. Your bike gets some protection from the elements too. $20/month