HT5048: About the OS X Lion v10.7.3 UpdateLearn about About the OS X Lion v10.7.3 Update
Currently Being ModeratedApr 12, 2012 8:17 AM (in response to andreas28091976)
PhotoStream is purely a conduit whereby any photos taken by or added to any one device are ported to all the others signed into the same account. The photos are not visible online, cannot be individually deleted from the server, and can only be synced in toto, not selected ones; they are deleted from the server after 30 days.
As said, you cannot delete individual photos, but you can reset Photostream, deleting everything from the server. Please see: