[EricRiese]

I've thought about something like this. In my mind it all comes down to receipts. We need a system of ubiquitous standardized itemized and cryptographically signed digital receipts. That way everything you buy aggregates into your personal inventory app. Then making a posting is a matter of one click and one photo. The UPC in receipt means a full product listing can be generated automatically. This is crucial since most Craigslist posts don't have sufficient detail about the specific item model and specs. But with a UPC or equivalent that can be pulled in automatically.

Once postings consistently have UPCs attached, you can figure out the market price for everything and push that to people who own the product when the price goes up.

You can also push out product recall and class action lawsuit alerts.

The receipt would really be a proof of purchase, since it's cryptographically signed. So it could be used to make verified third party product reviews without the conflict of interest of the site also selling products.

You could hook your personal inventory database up to your social network to make a lending library with all your friends. Why buy something new when you can search all your friends' stuff and borrow from them?

[withinboredom]

Why do you need the cryptographic signature? Who needs to know that I was the original owner of a tea kettle 7 years ago that has been sold in a yard sale twice?

Absolutely nobody.

Having an actual UPC (which coincidentally stands for "Universal Product Code") that is globally unique would be extremely useful. Further if all the parts were listed in the UPC (so it could be easily sold for parts, or even if I was looking for part abc123, I could find what products it is in), would be far more useful than caring who owns it.

[EricRiese]

It's the merchant's signature. The buyer's info isn't part of the receipt as I envision it. It's necessary for some of the functionality I mentioned but not all.

Also you're assuming the receipt from one transaction follows the item. That's not necessary. Every transaction gets a new receipt. But you would want a history of receipts for a Rolex or car.

Picture this, I submit the item to Craigslist with my receipt. It's not posted, but Craigslist verifies it and puts a check mark on the post.

[withinboredom]

That doesn’t prove anything. It just means you had access to a receipt at some point. This is a human problem that can’t really be solved with technology.

[adampk]

What is the "killer app" for something that would take this enormous level of effort?

[EricRiese]

I just listed several as far as I'm concerned. I don't see it happening as a Y Combinator Silicon Valley ad supported startup. The best I can imagine right now is to pitch the vision and have standards bodies and industry groups collaborate on the standard and then maybe find some place where the government can dictate "if you do business with us, you have to use this tech". For instance using the receipts for tax deductions. Give a preferential rate for digitally signed receipts to pass back the cost savings of not dealing with paper. And then hopefully it grows from there.

[Freak_NL]

The market price for two used hypothetical coffee makers¹ (same manufacturer/type/age) is rarely the same. One has scratches, stood in direct sunlight for years, and has a few parts in need of replacing soon, the other was used twice and has sat in a cupboard ever since. Both work.

Besides, who keeps receipts for anything but expensive items that might need warrantee? Most people don't. Sometimes you acquire something through different means: presents, inheriting, thrift shop, etc.

And that's avoiding the huge privacy matter of buying something with a unique tracking number attached and linked to you.

1: I'll take mine without hypothetical sugar please.

[EricRiese]

Who keeps receipts? That's the point, you would if it was easy. It's automatic like keeping a email. I have all my credit card transactions going back years. It would be the same.

It wouldn't be linked to me as I envision it.