It's interesting how at least several of the failures were good ideas with bad timing/execution that others have replicated successfully.

iCab: Uber obviously was very successful with this ~same premise

Smart Charter: I assume you can easily book a private jet online now?

Founder's Forge: linking record-keeping and payment is what makes Ramp great; 10 years of fintech innovations made executing this much easier

Spark Innovations: this is basically the premise of Airtable