Many companies (and the US government) create fake social media (Facebook, Twitter etc.) accounts in order to make it look like people are talking about their product. I personally know several frum people who have done this. The question is, isn't this clearly forbidden because of gneivas daas?
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The source for the concept/prohibition of geneivas da'as is the Mishnah in Chullin 93b and the Gemara that follows. The common denominator in all of the cases is that one is causing another to be thankful or appreciative for something which isn't really there; thus "stealing" the other's appreciation.* It is not really relevant to most questions of business ethics.
*Example: Opening a fancy bottle of wine and giving the plausible implication that it was in a certain guest's honor when in reality you were going to open it anyway.