It has never occurred to me that a company (in this case, Kobo) would offer a preview that does include a sizable preview.
That seems incredibly strange to me. If I downloaded a preview that was nothing more than the TOC, basically, I'd be highly annoyed. Our previews at eReading.com will be supplied by a vendor; that's a subject we'll need to visit.
As a strategy it just doesn't make much sense, and from a customer service standpoint, it's somewhat of a disaster, actually.