I am an enthusiastic user of Kiva since a few months. I saw that Kiva is almost global for what concerns microcredit, but less so in other ways. For example, tax deductability is very US-centred.
I know that tax legislation is typically a matter that each State like to treat its own way. But I recently read that the European Court of Justice has stated that donations made by a citizen of one EU member State to an organisation in another EU member State is deductible as if it were made in the same (
http://curia.europa.eu/en/actu/communiques/cp09/aff/cp090005en.pdf).
I am not an expert but it could be possible for Kiva to chose the most favorable EU country and establish some sort of European operation there and give all its European lenders the possibility to deduct their donations.
Daniel