Essentially all assets, except perhaps gold^H^H^H^H commodities in your physical posession, are numbers on a computer screen. Even land ownership is controlled by records kept by local governments.
This is clearly true, but the scenarios in which it becomes a problem vary. In an isolated case of data loss/corruption that leaves the title to your home up in the air, there would be other sources of data to appeal to (records at lenders who had paper on the property, etc.) In more apocalyptic scenarios, even your on-hand physical assets won't be good for much (you can't eat gold).
Sure, but the person I was talking to wasn't talking about data loss. He was talking about asset seizure by the state. If they're going to seize my 401k they're just as likely to size my rental property.
And ya, in apocalyptic scenarios the value of assets could swing wildly. I've seen Mad Max though. I'm not buying gold, I'm stockpiling guzzoline.