A few years ago I was reading "Growing a Business" by Paul Hawken[1], in which he shares his experiences in entrepreneurship (which are quite dated, but interesting). One thing that stuck out to me was that in his first business, he used $1000 to get up and started, and in the latest one at the time of writing, had used over $100,000. He said in the first he would have felt uncomfortable with more than a grand in the first experience and uncomfortable with less than a hundred grand in the last example.
I took away the point that the amount of funding needed to start a business is variable, and so are the needs of the founders. Founders shouldn't deal with more or less than they are comfortable with. Personally, I lean more in the direction you do, wanting a business to be cash flow positive before I took any outside capital. But that would be extremely difficult in many situations, and limiting yourself to having a product that is very small profitable now may limit your ability to build a product that is hugely profitable in the future. My thinking is that a founder needs to take time and evaluate carefully whether they should seek investment or bootstrap.
[1] http://www.amazon.com/Growing-Business-Paul-Hawken/dp/067167...