So just finished having a bit of a wrestling match after my clean Lion install. Everything went perfectly smooth, apps install, ilife 11, updates etc. Then I set about to turn on MobileMe and get everything synced up. I configured MobileMe as I have many times before, told it what to sync and when it asked told it to REPLACE the information on this computer. Everything (so I thought) came in fine... email account, transmit preferences, bookmarks etc. However, when I went into my address book, blank (except for my account and Apple). I thought hmm... let me check my iPhone... contacts wiped. No idea what might have happened, but something seriously went bump. Fortunately I air on the side of paranoid (having been bit by data loss) and had not only run a time machine backup to my server but also to a spare sata hard drive. Pulled it up.. and of course found the contacts folder in App Support/Address Book. Problem was, I couldn't find a way to import those files into the new Address book. The import function simply did not see it.... So I ended up getting on my son's 17" iMac still running SL (thankfully), dropped my Address Book folder into my profile on it, turned on mobileme sync and told it to replace the data on MobileMe. Presto... Lion machine pops up data changed, selected replace data on computer and my contacts appeared. Likewise my contacts on my iPhone popped right back up. No idea if this is an isolated incident or if anyone else has experienced it, but just to be safe, I would EXPORT your address book to an address book archive before doing the clean install!