I do think "oh, what a shame" is a negative response when not preceded by any discussion or other interaction with the mom.  My approach, when a mom says she is bottle feeding, or going to bottle feed, is to say I am a breastfeeding consultant, and therefore curious as to why she is bottle feeding.  Would she be willing to talk with me about it?

This opens a door between us, rather than slamming one shut, because she sees me as someone trying to understand her, not someone automatically making a negative judgment about her mothering.

There are some horrendous stories out there, and we can do a lot, just by listening, to alleviate what someone or something before us done to create a bottlefeeding mother.  And given a chance to unload, she may be more willing to try next time, or try again, or work at it longer.  It may help her realize that this time's lack of success, which might be the case, might be a baby-specific problem.  Or she might not yet be aware of some of the alternatives to bottle feeding, or ways to correct or supplement unsuccessful breastfeeding.

Do you walk up to a mother with a obviously physically challenged child (is that the PC phrase for crippled), or the mother of a Down's Syndrome child,   and say "Oh, how sad."   No, you don't.  So why do it for a child who is handicapped in this fashion -- by a bottle.  I know someone will leap in here and say, but this child wasn't born with a handicap, it's something mom is doing to him.  We don't know what handicaps might exist, physical, emotional, familial, etc.  But maybe we should find out, before we feel compelled to make any comment at all.

Chanita, San Francisco