Formpring is great. It’s similar to yahoo answers but the focus is on the expert, not the question asked. It’s a small detail but it changes the whole experience.
Technically you could use twitter in the same way, but Twitter has positioned themselves as a communications tool. It would just feel weird asking an expert multiple questions on twitter. But on Formspring the platform is all about questions, so the tone has been set for you and it feels natural.
It also appeals to people’s vanity like Twitter. Why doesn’t my school use this as tool for current students to keep in touch with alumni? As an alumn, I may not have time to be a guest speaker but I certainly have five minutes to answer a student’s question on there.
Many entrepreneurs are hunting for opportunities in new (and risky) markets when they would be better off looking at existing ideas from a slightly different angle.