Mathematics has a reputation of being unwelcoming, unforgiving, hard, and scary among most people. (Especially where I live, the USA.) I find this very unfortunate. On the one hand, laziness is to blame, students, even individuals sometimes don't put in enough time or effort to even come close to understanding even basic math-- As soon as the question is asked their first reaction is to give up. In fact, I think this is the primary cause of the problem.
However, a contributing factor is the very real, hostility beginners and newcomers face when interacting with mathematics enthusiasts and aspiring professionals.
If I had a dollar for every time I have see one person deliberately (or inadvertently) make another feel inferior and stupid using mathematics I would be very very rich.
I think any new user should be able to ask as simple as a question as they wish-- from the responses they will get a better idea of what is and what isn't 'doing enough work' on their end to merit community attention... they will also learn that this is not a homework help site. They may, in fact, grow to be excellent contributors.
(If you don't think this is possible I have seen many counterexamples. )
If they abuse the site we will remember and stop responding.
Yes, I do think think these questions should be closed, but I don't like the idea of a "lower bound" since it is not so much the content, but the way the questioner presents it that matters. And if they are closed we should be nice about it-- ie.
"Hey, James, you should take a look at some of the other questions to get a better idea of the way we share ideas here. More general question are looked on more favorable that particular ones since we are building a resource that we hope will be useful to many people... not just one person doing one problem."
I think we should be gentle and welcoming, in general-- and if the new person gets a little help before the question fades away so much the better.
In fact, we could have some kind of "close later" queue for things that we don't want clogging up the DB. This is not Yahoo Answers, after all.