Geographic e-publishing rights, not dissimilar to DVD regionalisation. Plus the fact that despite the fact that we all do it, I suspect that technically there might actually be laws against buying hard copies from amazon.com, or at least, Gerry Harvey wishes there was. (Well, moreso Mr Dymocks, et al.) Not unlike the fact that iPods were for sale even though it wasn't actually legal to have anything ON them for a good year or more...