I can't recall hearing/seeing any news stories locally about converters being stolen off cars.. not to say it doesn't happen.
I'm sure they are saved from crashed cars, etc...
maybe they just take the whole car?....
One of the guys on the Tundra forum had his stolen, he got it fixed and was ordering a skid plate (lead time then was like four weeks) and before his security plate arrived the thieves had hit his cats again. He installed the plates and felt safe till he came out one morning and his truck was gone.
The thieves had it towed, the cops found it four miles away in an abandoned parking lot, missing all four cats, the stereo, the seats, the tires and wheels and the tailgate.