This is nice list - the seven deadly blogging sins:
1. Using Free Blog Hosting Services
2. Ignoring the Basic Principles of Good Web Site Design and Usability
3. Being the Jack Of All Trades
4. Not Posting Regularly
5. Publishing Badly Written Posts
6. Spamming and Stealing
7. Failing to Establish a Personality

» The Seven Deadly Sins of Blogging