Tags are abused when one uses them to obtain a presentational effect, instead of using them to "annotate" their content.
Many CSS files you get on the web are redundant in many ways, for example they contain elements and subelements declaring the same styles or several classes (different names) with the same set of instructions.
I think that one of the major benefits of eBooks is that (potentially) the reader-user might provide "her own CSS" (*) and enjoy the book according to her preferences. (BTW, this was also the original idea behind the HTML.) Unfortunately, many publishers just want to "transpose" a paper edition into digital format, trying to reproduce it exactly. This leads, in many cases, to styling abuses. For example, I have seen a commercial EPUB of a novel (text-only) with an associated CSS with 400+ CSS declarations. These could have been reduced to less than 30 without impacting the "functionality" of the eBook.
To be fair, there are also cases where an essential part of the book consists in its typographical features, but then one might want to think about the opportunity of opting for other formats (PDF?).
(*) of course this is impossible to achieve in general, unless everyone agrees on using a common styling CSS structure. But, at least, if a CSS inside an EPUB is written with some logic, the user is able to edit it to tweak the appearance of the eBook. (I had to do this for several eBooks.)
Last edited by AlPe; 07-29-2012 at 06:30 AM.
Reason: it -> them in the first sentence