Personally, my problem is when there is not additional communication once the initial deadline has passed. If you were overly optimistic about a deadline - fine. It happens. I can readily believe it happens more with a game like AO. However if you're going to provide a self-imposed timeframe, be it a "best guess/hope" or a firm guarantee you should not let it pass without some explanation of what happened and what, if any, future date you have in mind.
Unfortunately for FC - once you start communicating timeline information to the community you have to keep at it. (Which has got to feel stupid saying "nothing new this week on items 1-9 of the list" over and over so I can appreciate the bind)