@tomr,
Sum Law: Just because a law is true for a finite number of terms doesn't *necessarily* mean that it is true for an infinite number of terms.
Again, I would argue that you're mishandling limits by separating n from 1/n in the computation of the string length. Take a look at the early terms of your new sequence:
1: 1/1 = 1
2: 1/2 + 1/2 = 1
3: 1/3 + 1/3 + 1/3 = 1
m: m*(1/m) = 1
Now, at what point does this sequence of ones suddenly decide to jump to zero (or any number other than 1)? This isn't an asymptotic curve that is approaching zero or anything other than 1. It's a flat line. You continue to make assumptions, arrive at a contradiction, and blame the one fact that every sane mathematician will agree on. Open your mind to the fact that something else is wrong with what you're assuming/doing.
If this doesn't demonstrate that your method is incorrect, then I don't know what will:
Surely you agree that there are functions whose limit as x approaches infinity is something other than zero - either a finite value or infinity (e.g. f(x) = 1 or f(x) = x^2).
But wait, that's not true. For if we take the limit of x*f(x)/x (which is really still f(x) if x != 0) and apply tomr's Infinite Sum Law of Limits (for which there are no exceptions), we get an infinite sum of zeros when we separate x*f(x) from 1/x.
Therefore, the limit of all functions is zero as x approaches infinity. QED
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"You will admit that the limit comes arbitrarily close but not equal to zero..."
No, the limit is zero - period. Individual terms (finite) are arbitrarily close to zero, but the limit IS zero. Look up the definition of limit.