I was going to ask a question and a box popped up saying that the question would probably be closed. I don't like it when my questions could be closed, so I didn't ask it. How does the input form scan it for subjectiveness, and what does it even mean when a question is subjective?
StackExchange scans for particular keywords and phrases in your question. For instance, try creating a new question (don't actually submit it obviously, just hit new question) and type in
What brands have the best X?. It will give you the warning. Now remove the word
best and try again. No warning.
I don't have a list of these keywords, unfortunately, but it really doesn't matter. It's just trying to be helpful, and won't always be correct.
At this stage, I'd say it's better to have more questions than fewer so we can get an idea of what questions are good, bad, on topic, off topic, etc. so I'd say you should probably go for it. At worst it will be closed, and that will be useful information to people asking questions in the future (public beta and beyond) as well.
I assume the Stackexchange software scans for some specific words or phrasing. This is based on experience of similar sites. Everytime someone uses those words or phrases this warning appears.