1. the gemara in chullin 94a forbids geneivas daas, deceiving a person, even a non jew, and the case there is not even a spoken lie, it is letting the other person walk away with the wrong impression. so is geneivas daas exactly the case where a business never technically lies but designs the message so the customer believes something false?
2. the shulchan aruch in choshen mishpat 228:6 paskens that a seller may not mislead in business, and if the item has a defect he must tell the buyer. how far does that duty go? does a seller have to fix wrong impressions the buyer made on his own, or only the ones the seller created?
3. the everyday cases: a permanent limited time sale that never ends, an inflated original price crossed out next to the real one, packaging that makes a product look more premium than it is, stock photos that look nothing like the actual item. which of these cross into geneivas daas and which are just normal marketing that no reasonable person believes?
bottom line: where is the line between selling and geneivas daas?
Thank you Rabbi, thank you very much.
Geneivas daas means actually misleading somebody. It does not mean every ordinary marketing technique that everybody already understands. Sale prices, crossed-out prices, attractive packaging, and similar things are part of the normal marketplace today, and consumers generally know how advertising works and can compare prices and products very easily.
The problem begins when you create or knowingly maintain a false impression that matters to the transaction. If a customer says in front of you, “I want this because it works at night,” and you know that it does not, allowing him to buy it on that understanding can be geneivas daas even though you never directly lied. But if the buyer simply imagines something on his own and you did nothing to create that impression, you are generally not responsible for every assumption in his head.
So the line is fairly simple: selling is presenting your product favorably. Geneivas daas is fooling the customer.