I'm not really brave enough to offer untracked mail to international destinations via eBay. It's not necessarily the buyers that worry me, though I wouldn't exclude it as a concern as different markets attract different people, it's more ebay and their meddling with things like delivery ETAs and dates, and requiring proof of delivery for an MBG claim (I get proof of post for all untracked mail I send OS via the lodgement terminals, but that only has a chance of helping me in non-eBay situations). Plus the FVF on postage makes things a lot harder for me since international postage is anything from $3-$50, and I baulk at the idea of paying an extra $4 or so in fees for the same sale just because the buyer lives outside of Oz. 

I do post that way daily to international destinations, though. I know this is not everyone's experience, but percentage-wise, my international sales are less problematic than my domestic ones. Sure, I've had some OS people send me some interesting messages, or get a bit antsy after two weeks (or sooner, sometimes - had a US buyer purchase on Good Friday, package posted on Tuesday and the order updated accordingly. Got a message on Saturday saying "still waiting for my order, I bought it one week ago" Had to tell her that it's not only perfectly normal, but that she could expect to wait a while longer -_- ), but I've only ever had chargebacks from Australian buyers, the instances of INRs are much higher from Aussies, and so is the percentage of buyers who try to claim their orders are missing items - I get about 5-6 Aussie buyers trying that for every 1 international buyer (I do have a much higher volume of Aus buyers, but I've taken that into account) .

The only thing you can really do is just test your market with some lower-value items for a while, and see what buyers are expecting and whether it's going to be worth the risk.