good list. This seems to happen fairly often when there are a bunch of drafts I am trying to get finished, and need to bang out a post so my loyal readers (that's you!) know I haven't keeled over and died over the weekend.
Fail to post for an entire year. Guilty as charged. It is advisable to post every day on a new blog, in order to garner interest in what you have to say. I agree that posts should come often, though I personally am not in the habit of posting much on the weekends. Monday seems to be a good day for readership, I'm guessing that this has to do with people reading when they get back to work or school. Saturdays are almost always the weakest days for my blogs, with Fridays and Sundays standing a decent chance of lesser readership as well, especially during widespread nice weather.
Make your readers jump through hoops in order to comment. Oftentimes, people will stumble onto your blog by way of a link from another blog or site, or from a search, and have an opinion on your content. Remember, it's these interactions that make a blog a blog in the first place, so avoid blogging in such a manner that a casual reader won't be able to comment without logging in. Make it easy for otheres to join in on the conversation, or risk pissing your readers off.
Post your everyday play-by-play. This one isn't set in stone, since many people have blogs which are specifically intended to keep in touch with family and close friends. If, however, you are blogging towards a slightly larger audience, you should really think twice before spitting out hourly posts with titles like I Finally Got That Crap Off The Wall Behind The Wastebasket or You Won't Believe What Color My Cat's Diarrhea Is Today. Posting often is important, but not if you're just going to write bullshit.
Don't Link To Anybody. I have somewhere in the vicinity of a zillion blogs in my reader. Every day I find posts that are relvevant to whatever it is that I'm writing about, or better yet, give me a fresh idea or two, and I sprinkle links to these into my own posts. If you're blogging, you should be doing this too. I could only think of two or three reasons why linking is one of the things that makes bloggers bloggers, so I defer here to Penelope Trunk's more comprehensive list.
Post Too Much. "But Chris," I can hear you wondering, "You just said that not posting enough was a problem. Now posting too much is no good, either?" That's right. In fact, I just finished getting rid of a bunch of feeds for this very reason. I enjoyed some of the content, but find that I simply cannot devote the time to wading through 30 posts a day from one blog. It makes me a little frazzled to open up the reader and see an insane number of unread posts. Anything exceeding 800, I generally consider insane. There was actually a small study published about this very topic earlier this year, see for yourself.