I first encountered him at privacy conferences, where he would, without fail, be the first person to the microphone anytime a tech company employee or government official spoke, and he would hammer them with the most uncomfortable, probing questions about privacy and surveillance.
The thing is, there are very few new faces on the privacy circuit. Many of these people had encountered Caspar before and had been on the receiving end of his unpleasant questions. If they gave a bullshit answer, the next time he asked the question, he would come prepared with material to respond. If they evaded, the next time he asked the question, he would mention how many times they had evaded it. He was relentless. It worked. He would ask the same questions over and over, until he finally browbreat them into giving an honest answer, on the record, in front of a room full of privacy experts, officials, and academics.
Caspar taught me a lot, both by showing me what to do, and what not to do. I really looked up to him, and now he's gone.
I'll miss you Caspar.