You need to go and read up on the transfinite numbers. Swizec is talking about what happens when you deal with a certain sort of infinity (a countable infinity) where there's a one-to-one mapping between the hotel rooms and the numbers.
In the transfinite numbers things that at first seem unintuitive happen, e.g.:
1. There are the same number of integers as there are even numbers. And there are the same number of integers as there are odd numbers.
2. There are the same number of rational numbers (fractions) as there are integers.
Here are some interesting questions on the Hilbert hotel which boggles my mind. Shortly, If you can keep as many rooms as you wish unoccupied, can you still claim your hotel is full?
(1) Example, if you can move everyone from N to N+1 or (N+5); and get an unoccupied room for new reservations, can you still claim anyone that your hotel with infinite rooms is fully occupied?
(2) Or is a fully occupied infinite-roomed hotel an oxymoron, or a self-contradictory dasein; which can not exist upfront?
(3) Or is it better to call an infinite-roomed hotel both fully occupied and fully available, a superposition of both predicates, or un-predicatable?
I think the mathematical definition of 'the hotel is full' would be 'there is a one-to-one correspondence, also called an isomorphism, between the hotel rooms and occupants'.
So, if the hotel has empty rooms, even if there are an infinite number of occupied rooms it is not 'full'.
On a side note: no matter how many occupants there are in the hotel one might argue that it was also 'empty' given that it can always accommodate a countably infinite number of new arrivals.
Honest question here; is the phrase "same number of X and Y" equivalent mathematically to "the cardinality of X and the cardinality of Y are the same"? I was taught "no", since "number of" doesn't apply to any of the infinities.
But perhaps I was taught incorrectly, or I have misremembered.
Well, Cantor's big thing was partly that he extended cardinality to infinite sets (http://en.wikipedia.org/wiki/Cardinal_number). The first infinite cardinal \aleph_0 is the cardinality of the natural numbers.
In the transfinite numbers things that at first seem unintuitive happen, e.g.:
1. There are the same number of integers as there are even numbers. And there are the same number of integers as there are odd numbers.
2. There are the same number of rational numbers (fractions) as there are integers.
3. There are more real numbers than integers.