So, MathOverflow is mainly used for posting research problems. Assume I have a research idea on which I want to write a paper. I developed it to some extent, but I am stuck somewhere and I post the current state of my problem asking for help here. Let's say that several nice and clever people help my research problem to be completely solved. Is it fine to publish the results, if they have actually done most of the work(at least as you did).
One option is to ask them whether they want to join you in writing this publication, but this makes the things complicated and sometimes you know in advance that the answer would be "No"(e.g. you're just a student, the people that answered your MO questions are some big names in math and the obtained results are far from good enough for them to accept putting their name there).
On the other hand, you have done some substantial work and waste significant amount of time, but you end up with nothing, if you don't publish. Of course you could and will cite all the MO questions in the paper, but is this enough in this case?