1gig or 10gig network for cluster?

[Koert Kuipers]

For a hadoop cluster that starts medium size (50 nodes) but could grow to
hundred of nodes, what is the recommended network in the rack? 1gig or 10gig
We have machines with 8 cores, 4 X 1tb drive (could grow to 8 X 1b drive),
48 Gb ram per node.
We expect "balanced" usage of the cluster (both storage and computations).
Thanks for your input,
Koert