Actually it is tax deductable in USA. You are lending but you must GIVE the money. YOU don't get it back. It goes back into your account to lend again. So if in America the initial "loan" is tax deductable.
I love this charity. You get to give over and over. And I like the idea that it helps people help themselves (the teaching to fish analogy and all that).
As per Prep's post only the contribution to Kiva's operations is tax deductable (and only for US residents) the loan itself is not tax deductable even in the USA.
In fact you can withdraw your loan money (Kiva credit) at the end of the loan process. It is obviously for this reason that the actual loan amount is not tax deductable.
Another fact is that the borrower pays an interest charge on the money borrowed. This interest charge is collected by their field partners (local coops etc) and funds the field partners operational costs. The interest charge does not get charged by Kiva nor does Kive receive any of the interest charged.
For me I see the Kiva process as helping / teaching the beneficiaries to fish rather than funding an handout and making people dependent on charity.
Cheers