The main problem that I have with the Kindle is not the lack of lending. What I want more than anything for the Kindle is support for ePub books, including DRMed ePubs. The Kindle would be enormously useful to me if I could navigate to my library's website, check out an eBook, and read it right on my Kindle.
If your library is anything like mine, supporting it would mean that Amazon would have to add support for Adobe's "Digital Editions" DRM scheme- which strikes me as somewhat unlikely, unfortunately (and by "somewhat unlikely", I mean that I'll be able to write a Duke Nukem' Forever review using TextMate 2 long before the Kindle supports ADE). This was actually a (small) part of my thinking when I was trying to decide…
Which would probably make a lot of sense at this point, given all the free reader apps they provide on various devices.
Hell, the system could be pretty sweet. Look up a book at Amazon, and Amazon could determine your local library system based on your address, check the ebook 'inventory' of that library, and if a copy is available, offer a library loan as an option. You wouldn't even have to go to the library website.