Being in touch with your consumers
One of the reasons that I abandoned my entrepreneurial pursuits is that I didn't feel that I was "in touch" with any potential markets. Now, there is an article in The New York Times by Matt Richtel entitled "From Lips of Children, Tips to Ears of Investors" which reports how even sophisticated and marketing-saavy venture capitalists are resorting to consulting with children, even their own children, before considering investments in the areas of Web 2.0, social networking, and other ventures which might be targeting consumers half or less of the age of the venture capitalists themselves.
In some cases you may be able to hire staff or consultants to clue you in, or take somebody else's word for what is needed to be "in touch", but ultimately you must have some accountability for being "in touch" with your target market.
If I do ever again pursue an entrepreneurial opportunity, you can bet your bottom dollar that I will have done a decent job of identifying a clear target market and verifying that I am "in touch" with that target market. But I don't expect to be in a position to pursue any such opportunities for another five years or more.