A neighbor on Wilton Avenue reported having her catalytic converter cut away from her Prius two nights ago between 2 and 3am. The muffler shop I visited today said he had several Sebastopol customers who'd experienced the same thing.
He told me that scrap dealers are not being policed well enough and there's a market for stolen converters and their platinum. Apparently specialized thieves are prowling neighborhoods in the early morning hours looking for Toyotas and Priuses.
At the recommendation of our great mechanic at TriStar in Santa Rosa, we took our Prius in to Johnny Franklin's Mufflers on Santa Rosa Avenue, and for $120 they made some modifications that will at least slow down and probably deter most thieves, who need to work fast. (I don't have any relationship with the muffler shop.)
There's a commercial product called the Cat Clamp that is more expensive, but it isn't offered for our older model Prius, so we went with the home-grown approach the muffler shop uses.
I don't know how active our police department is in patrolling in the wee hours, but I hope they are and just haven't caught anyone in the act yet.