Lots of websites did not show ad in their first or even after their seconds year. Youtube show ads 4-5 years after their initial. I think 1 year after Google bought it.
I think the site you are talking about will show ads in future.
So formspring seems to me to be into two things:
So I'm guessing that you're interested in at least one of those areas.
Q&A has a whole host of possibilities. But behind the apparent simplicity, there can be a lot of complexity. On the 'leveraging the web' front, there are hosts of players.
Ask Trueknowledge the question, "How will trueknowledge make money?" and (as of today) you'll get the answer, "We don't yet have an answer to that question," plus an invitation to suggest an answer.
Communities built around informed questions and answers really create value. You're here in one, after all.
If you have a great idea to create community like that, your main choice right now is targeted in-site advertising - now or at the point you have the scale and data. Which you could be one of the lucky ones who makes a living or builds a business from.
Or there's selling the data - which kind of sucks.
And somewebsites love to collect information and sell it! They might not necessarily be selling the actual email addresses or private data, but more data modeling stuff. I think a site like survey monkey could earn well selling their data.
So, you're asking us for a money making web site that will earn you a fortunate? If we had such an idea, do you really think we'd give it to someone else?