This is a problem that many systems have to deal with. It is usually handled by insurance and reputation. It can be improved by recordings of the delivery trip, and diagnostics run in the equipment at drop-off and pick-up. But we already handle this problem with rental items today without these fancy diagnostics. Mostly by just eating it.

The hijack problem (piracy) is one that's been talked about for autonomous vehicles. Remember the main driver today is the military wanting to move cargo. They have a few more options available than civilians, but it is indeed considered an issue.

The bots will of course transmit video of the hijacking, and their location, until they are smashed or put in a faraday cage. Hijacking is possible of course but it's not going to be a trivial thing. Quite possibly neighbourhoods where hijackers hang out will not have companies willing to run bots through them if the insurance rates get too high.

Dream or not, we'll see. Certainly people regularly find themselves running to the store for things they need, and would be happy to get a cheap deliverbot service at the very least.