(for the portuguese impaired, the text before the checkbox asks "Did you find this article interesting?". The checkbox label is 'Yes'.)
Now, I can understand what the person that designed this was trying to do (at least I think I do), but how can I say "No, I did not like the article". It seems that either I like it and check it, or if I don't I should just shut up and leave. More: if you decide that you do indeed like the article and check it, you cannot change your mind.
It seems that the possibility that someone would not like the article is too frightening to contemplate. Either that, or their tests with Safari where minimal.