Well, prop 13 necessitated the expanded scope of Assessment Districts, hence the mello-roos act. Having done some work on these CFD's, I'd have to agree that they have been misused by builders. The purpose of the CFD is to pay for the installation of infrastructure, new schools, and mainenance, however, the developer can throw any other fees he'd like into that pot, i.e. affordable home in lieu fees, etc (as opposed to forming an assessment district which would required justification as to which expenses are included).
i believe, if a developer wants to maxamize their benefit of the CFD and drive the prop tax rate to near 2%, that should be reflected as a discount in the home price, however, during the peak of the bubble, this was probably not the case.
But before you completely blame the developer, a public entity has to approve and vote on creating a CFD issuing municipal bonds. Unfortunatley, that public entity could be a school district or water district which developers often turn to.
Another issue is the stability of these municipal bonds related to mello-roos districts, i think there is a minor concern that some could fail, especially in the inland empire, where bonds have been issued but no houses were built, no houses means no residents and a bankrupt developer means no tax payments, fortunately, these are all insured by mbia etc , but as we all saw last week, there are still some jitters there. Again, this is something that happened in the 90's.