I should hope that is illegal to lie during such a transaction. Real estate disclosure laws don't cover that, though. They cover information you are required to volunteer to serious buyers. In the absence of such laws, you would not need to say anything about the state of your basement unless the buyer specifically asked.

Exactly. And that's why we have those disclosure laws, to make it against the law to take advantage of the fact that a buyer didn't think to ask a particular question.

You should be able to buy a stock without having to ask the seller "Hey, did you just get a heads up from the CEO that this is going to tank?"

There are lies of commission, but also lies of omission.