That's a great question. We built an application for Kiva staff that
uses the lender ID and as it turns out, a lot of them don't know this
either! I would expect only power users really know what this is.
However, what you can do is ask the user to paste in the URL to her
Kiva profile (or "lender page"). From there, you can just parse out
the Lender ID. It turns out, this is how we did this with our
application for the staff as well.
Cheers,
skylar