There have always been bad questions, and now that you bring this up, I think we should be doing more in the user education department.
First up, I'm not super enthusiastic about anonymous users being able to ask questions. Stack Overflow has disallowed that for a while; it might be time to think about doing that here too. I say that not only because I think people should have at least a shred of investment in the site, but because I frequently see question edit suggestions submitted by the same person under a different anonymous account. If login is required for that feature, people will be dramatically less likely to "lose" their questions.
Then, there should be more information presented to new users when asking questions. I know there are links to the help center on the Ask Question page, but they're not nearly obvious enough. Also, due to the wide audience of the site, we get boatloads of people flooding in who don't understand the Stack Exchange model. The tour does a little to help this, but not everyone reads the tour, and I wish it was more specific about how we're not a forum. I'm imagining a checklist like this:
- What have you tried or searched for?
- Is your question specific and technical?
- Have you put effort into formatting your question well?
- Have you included all information necessary to answer your question?
Unrelated to questions, but there should totally be a more obtrusive warning the first time an anonymous or new user attempts to answer a question, explaining that every answer must be an actual answer that adds new content.
If we want to get pretty intense, I'm imagining a quiz that new users would take before asking a question, asking them to identify which of a set of posts is appropriate for Super User. If they fail, a little blurb would appear explaining what was wrong with the selected post and how it could be improved.
Basically, we need to make it clear that Super User isn't just about getting answers, it's about building a top-quality resource, and that requires effort from everyone.
If I could give only one piece of advice to new users before their first post, I would boil down all my thoughts into this:
Look for a precedent.
That is, look for an existing, moderately-highly-upvoted, recent post that's in the same style and area as yours. Wondering whether your formatting is good enough? See what the community's response has been on posts that look like yours. Checking whether your question is on-topic? Look what people had to say about similar ones. If you can't find a well-received precedent, be very cautious.
As for what should be done now, we must continue using votes and comments as appropriate. Do your best to be courteous (I like to tell people what they'll be able to do eventually - usually in response to a comment posted as an answer). Wordsmith up some reusable "canned comments" if you must. I make it a personal policy to ensure there's an explanatory comment whenever I take a quality control action; it must be baffling and discouraging for new users to receive kinds of negative feedback they've never seen before without a human showing them what's going on.
Keep reviewing, keep explaining. People can only learn if we teach them.