I never expect warranty coverage on anything I buy on Ebay. I bought a Garmin GPS once that developed a problem. I thought about sending it into Garmin, but then I thought: "How do I know this GPS isn't hot? If it is, they'll probably confiscate it and cause me all kinds of problems."
Not that I condone nor would I knowingly buy stolen merchandise, but hey, you never know when buying from some anonymous soul on the Internet.
Anyway, my point is if you get a $3,000 frameset for $700 from a foreign seller, I think any expectation of warranty coverage is an illusion at best. What's their incentive to honor it? You can't neg a seller 6 months or a year after the sale, I don't think--especially if you've already given them feedback.