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Vivos do not have to invest money. VivaCrown holders invest in a venture like any new startup.
Viva is already involved in other projects and applications, which gives some credibility.

What gives the credibility for the exponential increase in the value of a viva crown though?

Especially given the influx of marketing from people who have a vested interest on steemit?

The viva is a crypto currency, for the time very volatile.Several people believe in the project.
As for @williambanks, he has been on Steemit since July 2016. He has been very involved with his posts, comments and suggestions. Now he talks about his project just as many others have been promoting their projects. The two projects are not in opposition, they can become complementary but they have different objectives.