João Novais, professor at Católica Porto Business School, in an interview with RTP, addressed the topic of Black Friday and some precautions to take: "Is it a great opportunity for cheap purchases or is it an incentive for impulse buying? Is it really possible to get good deals?" were some of the questions asked.
Watch the interview here, starting at minute 47:57 (Portuguese only).

Image (source): RTP Play - Website