Not own a $200 vacuum cleaner? What a laugh! Whoever
suggested that has never spilled anything, or had a
pet who came inside after rolling in leaves. Why would
I want to wait for a rental in those situations? And
one can get a pretty good vacuum for a couple hundred
dollars these days... what could a $2000 vacuum possibly
do any better?

And if one is renting an expensive, specialized piece of
equipment like a lathe or a band saw, then delivery is
only going to be a fraction of the cost. Robo-delivery
presents little advantage there.

Then there's the problem you probably haven't thought
of -- hijacking! What's to stop criminals to taking
the cargo, or even the whole vehicle to crack open
at leisure?

Consider also the liability issues.

"The deliverbot might be programmed to be extra-cautious
and slow around anything like a person."

Right, because we all know that machinery/software is always
easy to design properly, and always works as designed!

"if a deliverbot crashes into an inanimate object, it just
costs money"

Whoops, there goes all the savings, plus N months' profits!

A blog of crazy ideas indeed... another solution in search
of problem. This is the kind of stuff that makes it into
"in the future, we'll..." articles, but doesn't past muster
when a real-world cost/benefit analysis is done.