I definitely agree with Kathy Dettwyler's about thumbsucking and boredom.
Although not a fanatic on the subject, I made sure that during their
waking hours, my babies/toddlers were amply stimulated. Yes, I even
turned on the boob tube for these cute children's shows (not sure how
much they got from it, since they didn't learn Hebrew until they went to
pre-nursery school, but never mind), and put on records (good old Sesame
Street - my almost-24 yr old still remembers the lyrics!). Lots of walks,
shopping, playground. None of my kids ever sucked a thumb.

I have had this weird idea (OK, I have LOTS of weird ideas....) that
perhaps SOME cases of nursing strikes are because the baby is "bored"
with breastfeeding. I would like others' opinions on this. I believe that
SOME kids get bored by the same old thing, same old place, same old
chair, same old room. I like to suggest to moms that they nurse in
another room, change ambience, put on record, whatever.
Anyone?
Judy Knopf - and I almost never go for the "been there, done that", but
maybe there are babies out there more jaded than I   :-)