Stack Exchange has a built in system that blocks a user from asking more questions if their others have been low quality. From this Help Center page:
Stack Exchange has automatic filters in place to ban questions from accounts that have contributed many low-quality questions in the past. These filters help keep the quality of our sites high. The exact formula for the bans is not disclosed, but users are only banned if they have a significant number of heavily down-voted, zero-voted, or deleted posts. One or two bad posts will not cause you to be blocked from using the site.
As our traffic increases, we are attracting more questions from people who are not being responsible about them. I am probably more tolerant than most concerning questions based on curiosity from people who don't know much at all about space exploration, as I believe helping the general public understand the field is a service to the field. However, I also downvote questions that are very vague, poorly written, inflammatory, or confused more than most.
As a community, are we downvoting enough? It could be that our regulars are not aware enough that downvotes are a key part of the formula used to block users with a lot of low quality posts, until they show improvement. It could be that we are juuust getting to the point where we attract more attention from marginal people who aren't able to work with the format, and so we haven't adapted to that yet. So, please ask yourself where the line needs to be between helping out new people, and considering what is best for the site as a whole. This may be a good time for input on this.
Oh, one more thing, as it is pretty related - if you see the seed of a good question in a question from a new user that has a lot of problems, ask yourself if it is really best to help that user get points by making an extensive edit that saves it. Maybe it is. Or maybe you have enabled someone who doesn't deserve it to get a bunch of points, instead of you. That can lead to more problems down the line. It might be better to wait until that person has demonstrated the skills necessary to participate here before helping them out like that, or more valuable to the community for you to get those points, by asking the question better if the original is not fixed by the asker and is then deleted.