Can a swarm attack an adjacent creature, or must they occupy the same space as a creature to attack them? Let's consider the regular "Swarm of Teeth" attack of a Rat Swarm for an example: is its reach 0 or 1?
I've found rules saying that (emphasis mine):
A swarm can occupy the same space as another creature
And that tiny creatures have 0 reach.
I haven't found 4th edition rules saying what the default reach of swarm creatures is (regardless of the space they occupy). So, what is it?