Some NL sites I frequently visit were also unreachable a week or so ago. After research from a tech site that got hit, it appears that someone paid about 40 euro's to have a stress test website attack several domains for a day. No questions asked by the stress test website to see if the person paying for the stress test had anything to do with the requested domains...they just take the money and do their thing. The guy who paid for it was eventually caught, because he started to provoke/brag to one of the admins of the tech site through IRC.