Yes, of course if you make up your own tags for just about everything, that would suck (as tempting as it would be to use “bq” instead of “blockquote”, seeing how there is “q”…) I pay too little attention to accessibility anyway (who doesn’t :/ ), but I don’t want to make it worse for no good reason.
But what about d instead of div? and s instead of span? those have no semantical meaning anyway, right? so why use 13 or 11 characters where you could use 7… times a billion! It’s mostly because I’m playing around with making my own CMS, so these things “pay off (a little) in bulk”, and it’s at least thinkable to change back again without dying inside. Otherwise I wouldn’t bother, but I love shaving bytes off here and there :D