I think Wufoo solves a REAL problem - Collection of useful data. That's why it appeals to businesses and enterprises.

Whereas Formspring was more like a third party Facebook status box that served no real purpose (Their slogan was "Formspring is the place to share your perspective on anything."). The difference lies in the target audience - One was aimed at the consumer and the other at the enterprise.

Oh, I didn't know that. I thought they were a generic form site that pivoted into surveys.