Seems like the age is the thingI am glad to read these posts because it seems like we are all going through the same thing at around the same age (mine is 16 months) -- I think it is part of their developing awareness of self and of self-will, and as such should be a great thing, despite the added laundry. I was especially interested to see the other posts about kids hiding to poop, as this happens with us a lot lately -- him hiding sort of mischievously is one of our signals now! And he will only poop on toilet if I put him on right as he is pooping anyway.
We are not die-hard EC-ers-- as I wrote above, we use diapers but give lots of nakeybutt time and started him pooping on toilet much of the time at 4 months without anything systematic about it. I know that he is very aware of the whole thing, and that his hiding and refusing is all part of that awareness, coupled with this developing will and self-awareness. So I've decided to just continue trying and not to get crazy about it, let him use the floor and the sink and empty tub sometimes if that's the only places that will work, to assume that anyway it will work only about half the time but that, once he gets past this stage, esp once he is more verbal, it will be a zillion times easier to get him using the potty -- and will happen much earlier -- than if we hadn't done this.