Actually, it's your assertion that is not quite true.
It certainly used to be the case that "We give Field Partners the option to cover [...] entrepreneur defaults." [1] And there was indeed evidence at the time that Field Partners were doing just that. [2]
Although they have removed this explicit wording, it isn't clear that doing this is no longer allowed, and there is some evidence that the practice is continuing: Only 7 out of 128 pilot or active Field Partners report a default rate of more than 1%; indeed, around three-quarters of them report a default rate of 0.00%. [3] Frankly, these statistics are unbelievable unless we accept that most Field Partners still cover entrepreneur defaults.
So if the end-borrower defaults, you might lose money. But rather more likely is that the Field Partner will cover the loss themselves as an operating cost, not report any of this to Kiva, and you will be none-the-wiser.
[1] http://web.archive.org/web/20091117123031/http://www.kiva.or...
[2] http://blog.givewell.org/2009/10/13/kiva-repayment-data/
