second, if tackling the tail from the right end seems to take too long (either because the business opportunity is gone by then or by lack of patience), a 2 phase approach is possible
having a long tail business in mind, start with the sweet spot core business. after gaining grip there, reach out to the tail. amazon did start to sell books with the differentiators of free delivery, consumer reviews and easy search in the beginning. those provided an outstanding new shopping experience. successful growth in the core business brought in investors, closing the first phase. only after that, in phase two, the long tail got explored. (an similar approach can be expected with their web services.)
this requires a business, where competitive advantages already exist in the classical core business – and not only in the long tail. in that case, write your business plan, build your working prototype, bring along customers and core team. then approach venture capital (preferably through introductions).