Thanks for the interesting responses to the original post. I know the subject matter often ignites heated discussion because most folks feel strongly one way or the other.
Like all contracts, a cruise contract is a two-party agreement - among other things,
the cruiseline promises to provide certain services and amenities; among other things, passengers agree to pay for said services and amenities and abide by what Kuki referred to as "suggested rules of behavior." I think we'd all agree It's not unreasonable to expect the cruiseline to hold up its end of the bargain. As a matter of fact, these boards are plastered with complaints from passengers who object to various cruiselines falling short of the mark, and most folks who feel they've somehow been "cheated" expect to receive remunerarion of some kind in exchange for their trouble.
Yet on the flip side, many passengers (IMHO, including those who ignore the dress code because it's their vacation, they paid for it and they can do as they please regardless) think it's perfectly okay for them to pick and choose which portions of the "agreement" they will abide by. The suggested dress code does not come as a surprise to any passenger - it's clearly stated in marketing materials and in the cruise documents received prior to sailing. Those who book on a line that has an evening dress code with the full intention of ignoring it, in effect make a unilateral decision to ignore certain provisions of the cruise contract. Just imagine if the cruiselines took the same stance!