DD used to go 1-2 weeks without pooping, and she got uncomfortably gassy and I felt like it wasn't good for her. I've taken her for lots of craniosacral therapy, and now she usually goes every 3-5 days.
I've heard from many sources that bm is efficiently absorbed, and there's nothing left to poop out, so no biggie. And this may be true, but I've always felt that at least for my dd, it wasn't good (just my gut feeling). She's always been super gassy and had digestive issues (we had to stop co-sleeping because she was gassy and would kick me in her sleep -- the whole night). Both her chiro and holistic ped also feel it is not good, and say she should be pooping at least once/day, as pooping is one of the major ways our bodies have of eliminating toxins.
Starting this week, at the direction of the holistic ped, I am starting her on probiotics and two homeopathics to help support her digestive function (FYI, she is still primarily breastfed, with tiny tastes of fruit once or twice a week). So hopefully that will help!