For me, disconnecting and uninstalling cloud related apps such as dropbox/google enterprise/social media is more than 50% of sensitive data (personal/financial/work), the rest involves the thousands of pictures stored in phone (uploaded automatically to dropbox but kept in phone). It literally takes 10 minutes to do the above, and to get it back, just log back in and another 10 minutes everything will be back onto the phone.
The rest is a little more problematic.... contact list/call logs/sms logs/chat which, depending on the phone, is hard to delete.... not sure if anyone have any ideas for this part.
I feel CBP can compel/coerce travelers to unlock their phones to examine contents, but it'll be a million years before they can get passwords to look at your cloud/email data.