I'll be honest, I have and still do enter supposed projects into OmniFocus as a 2-3 word task. The reason is that when that project idea comes to mind, I don't really have the luxury to stop what I'm doing, flesh out the project, and make sure the flow and the metadata is correct in OmniFocus.
This happens to me all the time as well. Turning a loosely defined task into an actionable project is difficult. You need to stop and think it through. You need to ask yourself a lot of questions. It takes time.
It used to be a pain to have to think about this for every ambiguously defined project disguised as a task I had dropped into my OmniFocus library.
However, after listening to Merlin Mann's OmniFocus setup talk, I took his advice and I've found it much easier to deal with. He said something along the lines of "think in the Inbox so you don't have to think when you're doing". This is good advice. I now drop these loose ideas as a single line into my Inbox only. They never get into my library until I've fleshed them out. That means it might sit there for a week, but it'll get looked at during my weekly review and it won't be something I look at, and have to think about, when I'm in doing mode.
My Inbox is where I process ideas/tasks/projects. My Library is where actionable stuff goes.