There are quite a few people out there who would enjoy working out on interesting questions. If you already know the question or have solved it previously you just give the solution and admit it that you had seen it earlier. But more importantly its about the thought process and how you got to the answer.
"Similarly, I wouldn't even bother to bring in a candidate who transcribed his interviews elsewhere." - Well there are gazillion blogs and books written on technical interview questions including by ex google, msoft and apple employees. So is it really that bad that a sophomore student decided to blog about it for the benefit of fellow students.
It's bad for the same reason that leaking a midterm you just took for the benefit of fellow students is not helpful for those trying to conduct a test.
"Similarly, I wouldn't even bother to bring in a candidate who transcribed his interviews elsewhere." - Well there are gazillion blogs and books written on technical interview questions including by ex google, msoft and apple employees. So is it really that bad that a sophomore student decided to blog about it for the benefit of fellow students.