Well, generally I have ideas popping into my head on a regular basis. It's a very involuntary process. But when they're not doing that, then it's like I can't force it, or even try to brainstorm, because nothing comes. It hasn't always been like that, but lately it's become harder and harder to come up with something of interest.
Then there are some topics that I want to touch upon, but I can't get it to come out right. That's probably the most frustrating—when it makes sense in your head but it doesn't come out that way in print.
In addition to that, I've got a couple I want to do, but I know that there will be people within our circles who won't like what I have to say. When I know that's the case, I tend to worry too much about the words I use and the post tends to lose any impact or effectiveness.
So, there you go. I'm not so fond of lists, at least not for topics. They become restrictive, like I'm forced to do them, and that ends up feeling like work. :)