In Australia, yes, rabbits do bring bad luck (and myxomatosis--at least to the rabbits). :( But I suspect ptero's family doesn't live there, in which case those twitchy noses might actually be beneficial in some way...?
I would feel weirder mumbling "bilbies?" at my family members than mumbling "rabbits," but now that the possibility's been raised... Hmm...
She, I wonder if it got started in the same way that the rabbit's-foot-as-talisman did. And perhaps rabbits are considered good luck because they were an important protein source for people who lived (or poached, whatever it may have been called in their respective cultures) off the land.
There's a family tradition that if, on the first of the month, the first word out of your mouth is rabbits, you'll have good luck that month. Around my house, every time a new month begins, you'll see my family stumbling out of bed and greeting each other with a mumbled "Rabbits?".