One example does not prove this at all. It simply proved that no one wanted Freicoin. They might want something else with that property, but with some other differences.
I have to agree with Daniel on this one. He proved fairly rigorously why demurrage-based currencies must fail, and nobody has produced a refutation stronger than, "Maybe if I hope hard enough it will work!!!"
http://themisescircle.org/blog/2013/08/22/the-problem-with-altcoins/Freicoin is an idea whose time will never come. Since it rebukes buyers, it resists ever having value. Freicoin is thus not so much a scam but more an abortion. Its ideals are so refined that they eschew the merest chance of affecting the real world. Perhaps it could be taken as some sort of absurdist parody, which would be brilliant. I hope that is true because otherwise it is just too sad.
That's essentially identical to the frequent argument that deflationary currencies can't work because no one will spend them (or, in his words, it rebukes sellers). Both are wrong.