If we penalize people for trying to help by assuming their help is intended to farm rep, then we discourage people participating in questions that might be on the borderline.
Let’s say a genuine novice user asks a bad question without realizing it, such as "how do I upload a video to my site?" without specifics (encoding, whether he/she means hosting it on a web page, etc.) And people try to clarify, or at least point this person toward a book that could help them learn the proper terms and the differences between hosting and using a 3rd party service a bit, and come back later, then we are working against the idea of an exchange of knowledge. If this person gets no response, they walk away, learning nothing, and might never come back. This seems counter to the mission of this site. On the flip side, if people do not answer fearing rep-damage, they might not earn the rep they deserve for being helpful to even the clueless. In short it would cast a chilling effect over the site by discouraging participation in answering stupid/bad questions, and people who need answers would suffer.
Does this negative rep for answering bad Qs also discourage faming? Yes, but I think the damage to participation would be greater. Especially for duplicate questions. This idea would be akin to a teacher being penalized for answering bad questions. You might as well just post links to books in the extreme case. The idea is to exchange knowledge, & doing anything to damage that as a way of improving the quality is a bit like chopping off a hand to mend a few broken fingers.
I think a rep rollback, or the other commenter’s idea of catching the rep before it is permanent for obviously farmed Qs is a better solution, that won’t damage the site’s quality in the process.
I get questions each week from people in person or on the phone that tells me they haven’t grasped the basics of how networks or systems works. I help them by explaining that their preconceptions are wrong, and try to explain how things actually work, without a lot of tech jargon — like equating that 4GB of DRAM to the size of a desktop and the 2TB of HD/storage RAM as a filing cabinet to illustrated how working from a filing cabinet (pulling out one page at a time then putting it back, then pulling out another) is slower than spreading multiple pages out on a desk.
So, they learn by showing them how things are connected. After they grasp the basics, they have come back to me with good questions, such as “for a gaming computer, what is more important, the speed of the CPU or the quality of the Video Card?” or better, “Why is a dedicated video card better than an integrated one?” (Answer: no shared RAM). They know a little more, and I have less handholding to do. So, helping novices “level up” is a win-win IMO.