[tlunter]

The Microsoft version doesn't hide a local copy. The file still exists in the FS, just when run/opened, it should pull down the copy in place and open the now downloaded file in the correct program. This could be done with a similar feature to selective sync, and enabling this feature for certain folders and always syncing other folders.

[ghaff]

I was referring to the implication that the only actual copy of the file would seem to be on the cloud service in this scenario. ("I'm not going to pay for a TB of storage until I can moves files I don't need on my SSD anymore (ie RAW photos I've developed) into Dropbox and have them removed from my computer seamlessly.") Which may be OK but not necessarily something I'd be comfortable with.