There is no reason to think that we are alone in the Universe. At the same time, there is no reason to connect the Tunguska event with extraterrestrial intelligence. No trace of radioactivity was found in the Tunguska site, so that Kazantsev description should be abandoned. Nevertheless useful ideas can be found in good science fiction stories, as "Vzryv". For example, Kazantsev was the first who explained by an explosion in the atmosphere the lack of fragments or impact craters in Tunguska. Many years after, this idea was recognized as a good explanation of many Tunguska effects.