What happens to spam questions like this? Are they closed or just simply deleted? I know that spam answers are deleted. Are questions treated differently?
They are deleted. This even happens automatically, once a question has gathered a sufficient number of spam flags.
Closing questions is meant for:
- Giving the OP (or somebody else) the opportunity to improve a badly worded or an off topic question. If such bad questions were deleted, the opportunity wouldn't exist. If they were left open, waiting for improvement, they would gather answers aimed at the original wording instead. Closing avoids both problems.
- Involving the community. Everybody can (and is encouraged to) partake in closing and reopening questions, and editing them into shape.
- Transparency. In practice, only a small part of people who see a question take an action concerned with its closure, reopening, etc., and these people are often moderators or encumbent high-rep users. Keeping a closed question around before deleting it ensures that everybody can see what is happening with it, who is making decisions and why. It allows a discussion on marginal cases.
Once a closed question is old enough that there is no more chance of it ever being reopened, it is supposed to be deleted. We are less stringent about it here on Cooking, where we aren't swamped with old questions, but this is usual for the SO network.
Spam questions don't need such protection mechanisms. There is no chance or reason of improvement there. The community gets its chance to participate by flagging. And besides, they are dangerous - as long as we allow a spam link to stay up, we are aiding a malicious spammer. So, they don't stay around closed-but-visible, they get deleted by the system once enough humans decide that they are spam.