The Wikimedia Foundation is an "ANBI registered charity" [1]. It means that Dutch people may deduct their gift from their income.
In the Netherlands there is much more to tax deductibility, making it easier to deduct money for taxes even more and increasing the amount of money that may be had by the WMF..
At the time when the WMF itself became registered as such, it was clear that it is possible to make it an European charity and by consequence make gifts in the whole of the European community tax deductible.
I have in the past reached out to the WMF about this topic. I did not get any reply. It is certain that the process can be optimised for the donors and for the WMF in a meaningful way.
PS I am professionally involved in raising funds for charities in the Netherlands. Ie I am not clueless.
Thanks, GerardM
[1] https://wikimediafoundation.org/wiki/Tax_Deductibility/en#.C2.A0Netherlands