Will my ringtones for individual contacts be erased on my iPhone if I sync it with MobileMe?

I want to use MobileMe with my iPhone but I have to replace all the Contacts on my iPhone with the MobileMe contacts. Will this erase my ringtone settings for each individual contact? I don't want to have to go to each person and assign them a ringtone again.|||It might because I don't think itunes syncs that information into address book.