The rude thing is to not offer any reward in return for you, if you agree to their request.
It's just saying they want to take advantage of you if you fall for it. Making such a request means that they are happy to take advantage of you as long as you let them. Is that unethical?
Think of it this way: You own a truly valuable stamp but you don't know its value. Then somebody who knows its value offers to exchange it for their stamp of much lesser value, without telling you what they know about its value.
It may not be unethical, businesses are based on such behavior. Buy low and sell high to make a profit. But when you see such behavior by your friends or neighbors or colleagues, be aware. They are the kind of people who are happy to take advantage of you.
Hmm, I see a problem with this analogy in that the person selling the stamp is at an unfair disadvantage due to that information asymmetry. It's actually unethical and sometimes even illegal to do this in the stock market, especially if the knowledge wasn't publicly available.
I think askers sometimes feel put off by guessers, because you can't inherently know what the other person thinks is a fair request -- unless you're in a high context environment (which most askers won't be as familiar with). So from their perspective, guessers are doing a bit of insider trading ... only they know what's of value to them. It's frustrating from the askers POV because the counterparty seems less than transparent about their true intentions.
Of course, from the other side of the coin, the asker is ignoring a million cues that are obvious to the guesser but meaningless to the asker who doesn't even know to notice them.
It's just saying they want to take advantage of you if you fall for it. Making such a request means that they are happy to take advantage of you as long as you let them. Is that unethical?
Think of it this way: You own a truly valuable stamp but you don't know its value. Then somebody who knows its value offers to exchange it for their stamp of much lesser value, without telling you what they know about its value.
It may not be unethical, businesses are based on such behavior. Buy low and sell high to make a profit. But when you see such behavior by your friends or neighbors or colleagues, be aware. They are the kind of people who are happy to take advantage of you.