I'd like to backup my messages on my MBP to iCloud just as I do on my iPhone. How do you do it on a Mac?
Because you are already signed in to your iCloud account (or you wouldn't be getting messages), they are already in the cloud. Scroll up in your message window and you'll see all of them.
Are you sure that's possible on your phone? How do you do it?
----------
Played around a bit...look in ~/Library/Containers/com.apple.iChat/Data/Library/Messages/Archive/
Messages are stored there in dated folders. You should be able to restore a particular file from your back up (Time Machine or other method). I really doubt there is anything stored in the cloud.
Yep. I go to Settings -> Storage & Backup -> iCloud Backup then turn it on and it backs up into iCloud.
I see. But to restore, you have to restore the entire device to a previous state just to get that deleted message back. And it's just a backup that happens to be stored in the cloud. Your Mac is backed up (hopefully) to a local hard disk. To restore your deleted message, just restore the file I mentioned in my previous post.
It's your responsibility to back up your Mac. Hard drives fail. They always have. Apple provides a nice interface called Time Machine to back up your machine. All you have to do is plug in an external drive and turn it on. If you operate without a backup you are tempting fate. If everything were lost on your Mac due to a hard drive failure, you'd lose it all.
Apple's Time Machine page
As for your messages, they are not backup up from your Mac to the cloud. If the conversation is also on your iPhone or iPad, you may be able to recover it from there. Otherwise, your "accidentally deleted" important message is gone.