One trope from advertisements, at least in the United Kingdom, is that new products are always much better than the previous versions. But in the attempt to underline the progress that the company's made, very often they go too far and outline all the terrible points of the old product.
Of course, this is a bad idea because new products are released so fast that the consumers remember the claims made about the old one when it came out, and are anyway still probably using them, eating them, and so on. The lie seems so obvious to me that either a) people must be really stupid, enough that the adverts still have a positive effect; or b) the advertisers must be rather stupid. Or both.
As reviews become more common on the internet, I hope people will turn to them more, though as we've seen from the spates of fake reviews, it seems that companies are more clever online than they are on television. Nontheless, when enough people review a product, it's possible to gauge the consensus; the disadvantage is that it takes a lot longer to get than just listening to what the producer has to say. On the other hand, people have been using word of mouth as the best way of learning about new products for decades or centuries, so the web is just an escalated version of that.
- An advertising fallacy