That's possibly the worst advice. NOT planning for expanding is a good way to have to rewrite your software later. Granted, it doesn't have to be overly-normalized, but my God... If you need to expand later, you better plan for it now.
If you know your message board needs to interpolate with say, several clients, then doing somethign like SOAP or the ilkes will be required before hand. If you need it to do RSS feeds, better not making it too disorganized, otherwise, you'll have to litterally punch it in later on.