Evil Daisy wouldn't bring any item of food or beverage and opt for flowers or little soaps or something inedible for a hostess gift. Let the hostess hem and haw about that one -- she'll appear rude and ungrateful if she expresses any disappointment about the gift. Bad evil Daisy
I don't mind as much at a true potluck if the organizer asks me to bring something specific or within a category -- like "please bring an appetizer, but just so you know Betty is already bringing a veggie tray and Wilma said she'd make hummus." I don't want to eat 5 dishes of the same thing anymore than anyone else does. The only exception would be if I was asked to bring something completely out of my budget, too time intensive, or I can't stand to eat it myself -- but I have no problem stating that and asking if the organizer could suggest something else. Luckily I've never run across that issue.