For various reasons, this is the first time in years that our household hasn't had a spare computer, usually an old laptop. When we have guests (the kind staying for a few days) who haven't brought along a computer, we just hand over the old whatever and say -- here you go.
To me -- with other items, like cameras -- the deciding factor is the person's experience. Once when I was living in western NY, a photographer friend in Hawai'i sent me an urgent email asking to borrow my D300 body (she knew I'd just gotten a D800) because she was in a jam, with work to do, some Nikon lenses, and a non-functional body. Of course I sent it to her because I had spent a couple of days working with her and I know she was a pro. I didn't get it back for more than a year (and didn't care) and when I did, it was in exactly the condition I'd sent it to her in. Recently, a high school photographer I'd gotten to know (we'd both won prizes in a contest) was going to Japan and didn't have a wide-range zoom. It was last-minute and we couldn't make the connection, but I offered him my 18-200 (which I don't use because I'm on full frame now) without hesitation. The kid would have taken good care of it, I know.
I get the privacy thing. With a computer isn't not important to me, because I always have a guest account and when needed I let people use the guest account. But for iDevices . . . well, that's why I don't have email set up on my iPad. If somebody wants to use it, I don't care. There's nothing importantly personal on it.
The whole borrowing thing is fraught, though. Years ago I loaned a guy my power miter saw and he used it to build an entire deck, and then returned it with the same (now dull) blade he'd gotten it with. I thought that was rude, but I didn't say anything (I should have, I know). I just decided that the next time he asked to borrow a tool, I'd bring it up then and require him to return the tool in the condition in which he'd gotten it.