It's a common complaint, and for 99% of sellers the paranoia, which it is, is unjustified.
Being Canadian I have little choice but to buy/sell gear outside the country. Too little product in-country and most of it was bought at inflated CDN dealer prices that many folks (justifiably) want to try and recoup. Have made deals all over US, UK, EU, Asia, Australia. Never been ripped-off.
While everyone has horror stories, they are few and they don't reflect on every Canadian, Kiwi, Aussie of Brit, etec., ever to walk the earth.
My only complaint/issue was with a US buyer (an idiot regardless of nationallity) who thought Canada = Idaho or Kansas and that duties and import taxes were somehow my fault.
As with all things in life - common sense (as a seller) and a little boldness (as a buyer) are your greatest assets:
1. Avoid ebay if you can. Forums such as this one FM and POTN are better because folks have reps they want to protect. Ebay sales from established forum members are fine.
2. Re: #1, try and stick to folks with lots of posts, reps and watch the board for awhile - you can tell who has a decent rep vs, just a verbose poster.
3. If a seller says US only - ask, politely anyway (unless they are VERY explicit in their listing). This works better from Canada -- for some silly reason geographic proximity seems to diminish the perceived risk of theft. Good luck getting $$ from a fellow countryman who rips you - let alone from across ANY border.
That being said, you'd be surprised how many folks will ship outside the US if asked nicely -and faced with a likely sale.
4. Use Paypal. Yeah it costs 3% or so (if CC-based) or $$ bank transfers. They're easy, fast & secure. If you can somehow set up a US bank account or work via a US friend, all the better. There is also always the risk with the mish-mash of US banks and regs that some securities won't be recognized - or honored in a timely manner (e.g. Canadian cheques).
6. Give/demand shipping using tracking data and frequent update emails during the deal. It does still surprise me how trusting folks are sending $000's ahead of seeing any product.
7. A 100% Fleabay rep does help.
8. Make it clear when buying from a nervous or newbie seller that you KNOW any import taxes, etc are YOUR responsibility. You'd be surprised how many folks never attended a Geography 101 class.
9. Don't ask folks to fudge import values - it just makes nervous buyers that much more so -- even though all your doing is trying to avoid getting soaked. Most Customs folks ignore 'gift' etc labels anyway. A business doing so could get stomped on if caught doing it. If the seller does it voluntarily (some veteran ones will), have a drink in celebration -- if it works.
10. Try Canadian or non-US sellers on a board first to build a rep if you can, they (I've found) typically are less nervous about selling intn'l - probably because they have no choice 90% of the time.
Be patient, don't get angry (it's tough when a great deal from paranoid seller walks by an honest offshore buyer with $$$ in hand) and slowly build a rep.
That being said, I've cursed like a Royal Marine at my iMac screen on many an occasion re: the frustration your seeing.