

Ways To Go Viral - pitdesi
http://techcrunch.com/2011/12/26/eight-ways-go-viral/

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kcl
The formula is given without explanation. You can rederive it without too much
trouble.

You can't use the common formula for compound interest because users are
assumed to send invites only once. Compound interest would assume they were
sending invites continuously over the cycles.

If you look at the number of users added each cycle (the top row) you can see
that it doubles each time. It's given by c0 times K^i, where c0 is the initial
number of customers, K is the virality coefficient (2 in this case), and i is
the i-th cycle.

Adding each of the terms up to i to the original c0 gives the total number of
customers after i cycles. So you get a sum:

    
    
      sum over i from 0 to N of (c0 * K^i)
    

which using an exponential sum formula
(<http://mathworld.wolfram.com/ExponentialSumFormulas.html>) gives:

    
    
      c0 * ((1-K^(N+1)) / (1 - K))
    

Multiply by -1/-1

    
    
      c0 * ((K^(N+1) - 1) / (K - 1))
    

and N is the number of cycles (given by t/ct in the slides)

    
    
      c0 * ((K^(t/ct+1) - 1) / (K - 1))

~~~
uzish
Thanks for expanding on that kcl. I wish I could go into that depth in the
article :)

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daeken
> A more pervasive example is the “Sent from my iPhone/iPad” signature at the
> bottom of every email you send from your iPhone or iPad. Yes, even Apple is
> using viral tactics (actually, I believe BlackBerry started that with “Sent
> using BlackBerry”).

As noted in "Founders at Work", Hotmail used this tactic with a lot of
success. I don't know if they were the first to try it, but they were
definitely the first widespread example.

~~~
uzish
Thanks for pointing to this. Wasn't familiar with this one but it is a great
example of using the "signature" tactic.

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thelongkahn
Am I wrong in thinking that G+ attempts all of these things and yet still
struggles, or am I in the wrong circles? Or is it that Google has yet to reach
a tipping point with their product?

~~~
uzish
I'd claim that the relative success they have so far is a result of them using
these tactics.

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OoTheNigerian
It was just a matter of time before the "Number Posts" made it to Techcrunch.
I am sure slide shows are not a far way off.

~~~
phil
This one seems OK though -- he's attempting a taxonomy and does a reasonable
job. They just made the headline sound like it was a fill-in-the-blanks top
ten list.

