FYI, in case you didn't know, ebay has a pretty unequivocal anti-robot clause in its TOS:

Access and Interference.
The Site contains robot exclusion headers. ... You agree that you will not use any robot, spider, scraper or other automated means to access the Site for any purpose without our express written permission. Additionally, you agree that you will not ... bypass our robot exclusion headers or other measures we may use to prevent or restrict access to the Site.

I don't know how agressive ebay is at detecting robots, though I'd imagine that if they catch you at the very least you'd lose your account. Maybe some other monk will post some first-hand knowledge of these questions.