If someone asks how to do XYZ, and you think doing XYZ at all is a Bad Idea™, is it valid to post an answer saying so? You aren't answering the question, but instead, arguing the question's validity. You could do this in a comment, but I don't think comments carry enough weight on occasion.

For example, I came across this today SO1176239; for those not wanting to link away:

I would like to build a wiki based website about professors, so that students can share information and check the reputation of the professor before working for him.

and I really wanted to post an answer that said, "I think this is a very bad idea". (In fact I did anyway, despite awareness that it could get myself flamed.)

Was I wrong? What should I have done instead?

If someone asks how to do XYZ, and you think doing XYZ at all is a Bad Idea™, is it valid to post an answer saying so? You aren't answering the question, but instead, arguing the question's validity. You could do this in a comment, but I don't think comments carry enough weight on occasion.

For example, I came across this today SO1176239; for those not wanting to link away:

I would like to build a wiki based website about professors, so that students can share information and check the reputation of the professor before working for him.

and I really wanted to post an answer that said, "I think this is a very bad idea". (In fact I did anyway, despite awareness that it could get myself flamed.)

Was I wrong? What should I have done instead?

If someone asks how to do XYZ, and you think doing XYZ at all is a Bad Idea, is it valid to post an answer saying so? You aren't answering the question, but instead, arguing the question's validity. You could do this in a comment, but I don't think comments carry enough weight on occasion.

For example, I came across this today SO1176239; for those not wanting to link away:

I would like to build a wiki based website about professors, so that students can share information and check the reputation of the professor before working for him.

and I really wanted to post an answer that said "I think this is a very bad idea". (In fact I did anyway, despite awareness that it could get my flamed.)

Was I wrong? What should I have done instead?

If someone asks how to do XYZ, and you think doing XYZ at all is a Bad Idea™, is it valid to post an answer saying so? You aren't answering the question, but instead, arguing the question's validity. You could do this in a comment, but I don't think comments carry enough weight on occasion.

For example, I came across this today SO1176239; for those not wanting to link away:

I would like to build a wiki based website about professors, so that students can share information and check the reputation of the professor before working for him.

and I really wanted to post an answer that said, "I think this is a very bad idea". (In fact I did anyway, despite awareness that it could get myself flamed.)

Was I wrong? What should I have done instead?