Yes, it states to change in settings but a number tried and found they were unable to do so--there have been a number of threads about this on Apple support. Some are afraid to "delete account" and the link about changing your Apple ID doesn't state so (some would say its implied LOL) but, as I said in the post above, I did delete the account (mine) on just my husband's Ipad 1 and added a new email and password to establish a different Apple ID so my husband's and my Photostream and backups on Icloud aren't merged. if you want to Imessage between two devices with same store ID you also have to have different Apple IDs and that's also not perfectly clear as to how to do that since that also has generated several threads in Apple support--and is a different process.
Frankly, I ended up turning off Photostream since I do a lot of printscreens for tutorials and thus have a lot of junk stuff floating up on Touch, my PC and Apple TV so until they implement a way to delete from the Photostream its not worthwhile at all for me. I also find that I prefer Dropbox to backup data because I can access it from any device, Apple or not, and decide what I want backed up. I do add some things in Goodreader to Icloud but it doesn't serve the purpose I prefer for backup that Dropbox, Box.net and other cloud services do so I won't be buying more storage from Apple whereas I probably will buy more from Dropbox.