I think a lot of people are getting too hung up on the fact that the application is specifically "hello world." The code is clearly buggy, even if you don't particularly care about bugs in this specific application. The author would have been better off not mentioning "hello world" as the application and simply said:

Find the bug!

    puts("This is a log");

I think everyone can agree that the above should be considered a bug in any kind of non-hello-world production code, for the reason the article mentioned.