This last group is amazon only. I do try to check the other sites and include the links when I find them (but, today I've been goofing off here, instead, so didn't check each one at the other stores).
I did see a comment in the other thread, that it's as easy as clicking forward on an email to put together these posts -- I wish! I used to check all the stores, but kobo is super slow since borders went under (at least, it is on firefox) and each one at B&N can take an extra minute to do the search, find the page, add a link, etc, so when I am short of time, I just skip them. Someone else said you might get a dollar a day doing this and that is, actually, much too high an estimate for most of the other stores (B&N might yield 50 cents on a good day, for example).