Not an answer to your question, I am affraid. Just a bumb because I really want to find out how to reset my iCloud account too. I migrated from mobile me and it is a complete mess. To get rid of everything in iCloud and replace it with what's on my Mac (which I've had to recover via Time Machine because iCloud syncing produced lots of duplicates and wiped all my contacts). Nice that it "just works".
Well, I spoke with AppleCare team. As per support responce, I need to manaually delete items from Contacts, Mail, Calendar, Docs and Find My iPhone. I can only reset Photostream from settings menu. There is no option to reset iCloud account instantly!
When comes to your's MobileMe migration issue ... I initiated migration before ... it's successful ... Can't merge MobileMe (now iCloud) with AppleID ... Then I login into iCloud with my AppleID to create both iCloud account and @me.com addresses. I hope this helps!
Thanks for the info. Yes, after restoring my data to pre-mobileme/iCloud state and ensuring that extra were backups in place I went to iCloud in my browser (while I was signed out of iCloud on the Mac). I deleted everything from iCloud. Then I signed into iCloud in the Mac's system prefs and let it do its stuff. Calendars worked out fine after a while but contacts were were not appearing on iCloud (but at least they weren't being deleted on the Mac this time) after disabling and re-enabling contact syncing a couple of times and resetting safari. The contacts were the same in the iCloud and on the Mac. So now it seems to be working.
After this flakey start though, I have to say that I am not filled with confidence that our data is safe in iCloud's hands (not that clouds have hands). So fastidious back-ups all round.
Thanks for your help.