Will the topic degrade into a heated debate that violates the "be nice" rule? Is it a topic that historically degrades in such a manner? Will the topic generate complaints from users?
Does the topic violate the rules of the ranch? Is the topic about cheating? about violating copyrights? Discussing specific companies? SPAM? Completely off topic to anything that is discussed on the ranch?
There are reasons behind the rules. And generally, most of the reasons are so that we can create an environment that is comfortable, and useful for the majority of the users. And unfortunately, sometimes, this means that we have to forbid certain topics, and ban some users.
Subhajit, Since a sync flood attack is a form of a denial of service attack, I think it depends on the point of view of the question. If you are planning to ask about how you can protect from one, that's cool. If you are planning to ask how to bring down an external site, it's not. As the discussion would have a very different focus and different answers, it is easy to tell the difference.