Great idea, actually. exif info is very easy to read, and companies are currently creating seamless solutions to track exif info/pictures from the same camera. However, if you process your eBay photos in Photoshop like I do, it will usually strip most exif info from the file.
I just opened one of my eBay pics in Photoshop and checked, it had generic exif info and some basic stuff about my camera. Nothing individual that I could see. But for good measure, use a delete program and process your eBay pics en mass after you create them for a bunch of listings.