I don't think what you're arguing would be a problem. From the article:

"Only when a file is shared from user-to-user (or with the Internet at large) does the DMCA check system come into play"

"Some thought the original file was deleted from the user’s Dropbox — that’s not the case, either. Dropbox just blocks the file from being shared."

Personally I think cloud services are super convenient and the downside for most people is really small.