Crumbs, I'm another one who needs to join the "bad parenting" club.
DH watches BBC Breakfast when he gets up to get ready for work. I tend to keep Breakfast on so I can see the headlines/local news/weather and then switch over to cbeebies whilst I get myself ready, do some washing up etc. We've probably already clocked up 60-90 minutes by the time we go out 
DD and I will then go out in the morning - toddler group, shopping, the park, a friend's house etc. Back home for lunch, then DD will have her nap.
I do try to keep the TV off in the afternoons, but there are some days when DD tends to be even more into everything than normal. It's exhausting to keep moving her away from the CD cabinet/bookshelves when all she wants to do is pull the CDs or books out, so I'll often resort to putting the TV on. I know perhaps I "should" engage her with something else, but that is easier said than done when I need to get on with getting dinner ready etc.
Just wondering whether parents who limit TV to 15 minutes (or thereabouts) per day are those who go out to work? I'm interested in what other SAHMs do. The days seem very, very long sometimes, especially when I haven't had adult company, so putting the TV on can be a god-send to enable me to have a little bit of respite.