I am willing to trade to Canada, no problem. I get a bit antsy when trades get big $$-wise, but I've done 2 large ones with AsymptomaticPyrexia for example that went perfectly.
Mailing in a plain white envelope takes a global stamp, which isn't that much more. Bubble mailers are more expensive, require a customs form, and cost a few bucks more but still manageable.
My big issues are these two:
1. It's an arm and a leg to do any sort of tracking or registration cross-border, and even then the post office cashiers will take pains to point out that there are no guarantees cross-border.
2. Everything goes through Customs as well, which introduces a black box between me and my trade partner that will add a delay of some unspecified number of days depending on what time of year you're trying to trade. I imagine the delay gets really bad around Christmas/Hanukkah but haven't had any in-person experience yet. I have a pretty good feel for how long mail will take between when I send it and when the other person can mark it received, but I don't have that sense for cross-border.
