This is actually a different issue relating to fraud. We've talked about this a bit in the past but the gist is we have our own fraud system on top of Paypal & Stripe. Any payment provider has their own checks in place but they all aren't adequate enough. When a fraudulent order gets past them and us, the seller ships the order and then Tindie is on the hook for the full amount once the processor notifies us it was fraudulent. Not a good thing...
To put some perspective on this, we have caught tens of thousands if not hundreds of thousands of dollars in fraudulent orders. These are orders sellers and Tindie are protected from.
Some orders that come in, flag us for a manual check. The catch comes when many people order a product with limited inventory and an early order(s) were caught by our spam filter for manual verification. Therefore the early customer's order was flagged for manual review - meanwhile another customer buys the inventory out from under that person. Not a good thing - and we agree its an issue.
This is really a tough situation because everyone is emailed once a product comes in.
One solution - batch the emails so everyone isn't notified at once. That way we slow the current problem.
Another - we deduct inventory totals for orders that were flagged by the system. Currently we do not, which is what gets us into this situation. The problem comes when people come to Tindie, see its sold out, but then we put them back in stock and then what should we do? Notify people again? Probably not the best solution..
However I'm open to ideas on this. We are trying to protect everyone involved from fraud (a good thing). If payment processors were more safe, we wouldn't have this situation. Unfortunately that isn't the case so we do have to act on top of their systems.