One of the trickiest things about selecting interns is finding just the right balance of a person who will be helpful, but who will also gain something useful from the experience.
I was put in mind of this when Claire Burrows, a graduate student and an awesome winter intern, just sent a lovely goodbye e-mail which included this line: "I feel like I achieved what I came for, plus had some excellent conversations (my next blog: talking cats who use sex as a weapon)."
Ah, Claire, you've learned your lessons well. Thank you for your help and good luck with your dissertation!