shrubbery - there's a dfference between the universe being infinite, and it containing an infinite amount of matter (ie planets). Plus, if you're defining 'infinite size' by 'you can keep going forever without hitting an edge', imagine that it might be curved in another dimension - like an ant wandering on the surface of a football.
So I find fault with your argument, to be honest:
1) is the universe infinite?
2) you've jumped from infinite space to infinite matter
3) if something is infinite, must it all be different?
To understand (3) - if I tell you that the decimal expansion of 1/3 has an infinite number of digits; I could use the same logic you've just used to say that it must contain every digit known to man, and every possible sequence of numbers... Just because it's infinite doesn't mean it is infinitely variable.
Having said all that, you could well be right (see anything on Possible Worlds. The Worlds might not be in our universe - depends how you define universe to be honest - but could be out there!)
And Douglas Adams is wonderful...
