Amazon Kindle's new lending library, and what it means for writers

If you've been on Amazon recently, you may have noticed that some ebooks are free to borrow, as long as you have a Prime account and a Kindle. I received an e-mail today inviting me to the program, saying that if readers borrow my book, I'll be compensated a certain amount based on how many books total are borrowed during the month.

However, when I went to enroll, a notice popped up saying my books "must not be available in digital format on any other platform during their enrollment." I guess this means no Smashwords and no Barnes & Noble.

Smashwords has been a huge promotional tool for me, especially with its free coupons I send to book reviewers, so I don't want to take my book down there. And Barnes & Noble has netted me sales for readers with the Nook. I could make my next novel an Amazon exclusive for a few months, especially since my books are now available for sale in other countries there, but I don't want to shut out readers with the Nook, or keep it out of book reviewers' hands.

I know Amazon is trying to sell Kindles, and the majority of my sales are from their site, but I don't like how they're trying to monopolize the market. I'd apply for enrollment for a reduced payout if I could keep my book on other platforms. Writers, what do you think about this new program?

Update: Smashwords has responded here.