Fantastic post! I just wanna share my personal experience. I remember when I was just starting out with my ecommerce site. a few months ago, i was having a hard time choosing the best products to sell online. I kept on surfing online to see what people are interested in, without even asking myself "what am i really interest in?". When i have finally decided on the product that i wanna sell, things got clearer.
On the other hand, i also agree that "you should treat your business as a business and not like your own personal hobby horse".. there are a lot of things to consider in starting an online store. For those planning to start an online shop, this page may just help you identify the important things you should consider:
http://storeberries.com/blog/2010/09/17/questions-to-answer-in-setting-up-an-online-store/