StackLead (YC W14) takes the hassle out of lead analysis

I don't know if this is built on the FullContact API, but you could very easily build the exact same thing with the FullContact API. In fact the company I work at did exactly that. Took us less than a week.

Smart arbitrage play perhaps but not very defensible, especially if your customers are the kinds of companies most likely to know about FullContact, which gives you up to 25,000 matches per month for $99 (vs. $19 for 300 with StackLead).