Probably using the lending as a way to hold onto/secure merchants to sell their wares, use their banking, etc. Wells, Citi, Chase, B of A all do that with large merchants. They give them processign at interchage flat, or even interchange minus, to secure their banking business (where the real mony is).

Amazon is now going to be "lending money" to merchants (too proud to call it factoring?). Obviousy a way to lock in the sellers and also help increase the sales on their website (for which they collect commissions).