Shiftybugger, thank you for starting this thread. I was considering using Coinabul, but the complete lack of accountability shown in Coinabul's response made me think twice. They are not going to refund your order because you bugged them after months of not receiving anything? Completely inappropriate response. I'd like to get Casascius to weigh in on this, he also a lot of experience sending insured orders paid for by bitcoin and I'm sure he would refund the order in a case like this.
Here would be my take:
1. I take the position that I only guarantee I'll send what was ordered. I do not guarantee anyone will receive what they ordered unless they pay for insurance, which in my case is only available with registered mail. There's not really another sustainable position to take without opening myself up to scams.
2. It is so incredibly rare for things to disappear in the mail that paying for insurance, in terms of expected value, is virtually always a waste of money. Odds of losing a package are easily more favorable than 500:1. It only makes sense for the most valuable of shipments.
3. One good way I've found to mitigate risk, especially with silver coins, is to split orders up into multiple envelopes and mail them on separate days. This also helps things make it through customs with the privilege of not getting flagged for special treatment. And that's how it seems is the best way to mail silver coins: in a boring envelope (mine are 15cm x 15cm, meant for mailing CDs/DVDs).
4. I probably wouldn't suggest to a customer whose package went missing that I was dealing with an insurance company or that my reaction depended on whether I was able to collect from insurance. As far as I'm concerned, if the customer didn't pay for insurance, then any insurance I might have is to benefit me, not them. Instead, I'd tell them to keep waiting, as it might eventually show up, or that I would let them know if I saw the package returned (which, oddly, has happened a couple times, many months after the original mailing, with the package notated "unclaimed").
5. I may, in my sole discretion, offer favors to keep people happy. The simplest favor I can offer to someone I'm forced to say they're outta luck is offering them a replacement order "at cost" without any markup, and throwing in freebies that might be valuable to them but are low cost for me. Then again, I have more flexibility in that respect than a bullion dealer, because I can pad my products with a healthy markup and a bullion dealer cannot while still remaining competitive. If I were a bullion dealer, I'm not sure what I would do, cause it's not like I could just throw in some free PM's to anyone claiming a loss and keep my business sustainable. ANd if someone came to the forums and alleged that I was a "scammer" as in this thread (as opposed to simply posting that they're disappointed they took a loss) I'd be the least motivated to offer a favor, just sayin.
6. If I were being accused of scamming by international customers (where registered mail is less efficient), to protect my reputation I'd probably switch my business to domestic only and/or require registered mail for everything, and only accept bulk orders from international resellers that I already trusted. That would be sad, but unavoidable if I did things that made it effective for scammers to scam me. Suffice it to say, I'd rather tell a few unlucky people that they're out of luck, because the odds are still overwhelming that most everyone will get what they ordered.